deploy.sh no longer starts units a live session already runs

`sync` on a box with a live session on it was unsafe in two independent ways, found by
preflighting the run rather than performing it. Refs #44.

**`enable --now` would have armed a screen lock mid-session.** The unit loop started every
`systemd-user/` unit whose `ExecStart` resolves. `swayidle-lock.service` on blankpad is
`enabled`/`inactive` — nothing started it, no swayidle process exists, `autostart.kdl` does
not launch one — so one `deploy.sh` would have begun blanking and locking the monitors while
the operator was mid-sentence. `live-sync.service` is `linked`, driven by its timer, and
`--now` forces a heartbeat commit at an arbitrary moment. A unit is now started only when
systemd reports it as nothing-yet (`""`/`disabled`), which is precisely a fresh box; anything
already installed is merely `enable`d. The state has to come from the **printed state**:
`is-enabled` exits 1 for `linked` exactly as for `disabled`, so exit status cannot
distinguish "installed, timer-driven" from "never installed" — the first version of this fix
got that wrong and the test caught it.

**`--check` output was being read as more than it can mean.** It prints `RELINK` for every
path the `zz` tier carries, even when the live link already points at the override
(`rules.kdl`, `keybinds.kdl`, `misc.kdl`, `autostart.kdl`, `.zshrc` all did on blankpad),
because the walk visits the base package first and reports the intermediate owner change.
The sentence committed in #43 — RELINK noise is "the sound of a stale override waiting" — is
too strong and is corrected: the line proves a pending change only when `readlink` shows the
live target is not already the `zz-$HOST` file, and `actions=0` is the honest summary. The
stale-override hazard #43 removed was and is real; the signal for it is the target, not the line.

**The dconf dump carried six of its 24 keys from another box**, none of them preferences:
a Firefox file-chooser `last-folder-path` of `/home/dank/Downloads`, a nautilus
`window-state` section, and `picture-uri`/`picture-uri-dark` pointing at
`file:///home/dank/.config/background`. The last five showed no conflict because blankpad's
live tree *already* held those `/home/dank` values — an earlier deploy wrote them here — and
a foreign value that agrees with live is invisible to any diff while still being wrong. They
are dropped; `picture-options='zoom'` stays, because it is a preference. The live wallpaper
URIs are cleared on the box as part of landing this (niri draws the wallpaper, noctalia owns
it, nothing reads a dead path).

`tests/deploy.bats` grows by four, over a stub `systemctl` — the real one on this box is
exactly what must not be invoked from a test. Red before: an already-`enabled` unit and a
`linked` unit both get `--now`. Green after, including the two directions that keep the
change honest: a `disabled` unit is still `enable --now`'d so a fresh box comes up, and a
unit whose `ExecStart` is absent here is never touched at all.

Verification: `bats tests/` 70/70, `kb-lint.sh omp-docs` 0, `kb-coverage.py` 0. The dump now
reconciles against live state with **0 conflicts and no `/home/` values in 18 keys**, proven
by key-by-key comparison rather than `diff` — `dconf load` writes only the keys present, so a
diff overstates the damage one way and hides it the other.

omp-docs/tools/dotfiles-deploy.md

@@ -25,14 +25,16 @@ is stowed last and its files replace symlinks coming from base packages.
 | `deploy.sh` (sync) | adopt identicals, link new, quarantine divergents into `.quarantine/` and replace them |
 | `deploy.sh --adopt` | like sync, but divergents are reported and skipped rather than quarantined |
 
-Two package shapes are not symlinks: `dconf/dump.txt` is loaded with `dconf load /`, and
-`systemd-user` units get `daemon-reload` plus `enable --now` only when their `ExecStart`
-binary resolves on the current machine, so a unit belonging to another box stays inert
-instead of crash-looping.
+Two package shapes are not symlinks. `dconf/dump.txt` is loaded with `dconf load /`, and
+`systemd-user` units get `daemon-reload` plus `enable`; a unit is **started** only when
+systemd reports it as nothing-yet (`""`/`disabled`), and never when its `ExecStart` binary
+is absent here, so a unit belonging to another box stays inert instead of crash-looping.
+Starting something already installed is what makes `deploy.sh` unsafe to run beside a live
+session — see *Never start a unit a session may already be running*.
 
 **The tracked unit is the file, not the directory.** A live directory can be a real
 directory and still be fully tracked, because every file inside it is a symlink into the
-repo (`niri` is 9 tracked / 1 box-only; `gtk-3.0` is 3/0). Any audit that classifies by
+repo (`niri` is 8 tracked / 2 box-only; `gtk-3.0` is 3/0). Any audit that classifies by
 directory mislabels the tree — classify per file with `readlink -f`. The live census and
 its classifier command are in [home-config-census](/inventory/home-config-census.md).
 
@@ -123,5 +125,62 @@ run and one unattended `deploy.sh` would have reverted the amber focus ring with
 quarantine and no warning. The duplicate is deleted in #43.
 
 Rule: a `zz` file exists only to differ. When base absorbs the change, delete the `zz` copy
-in the same commit — and never read `RELINK` lines from `--check` as cosmetic noise; they
-are the sound of a stale override waiting for someone to run the tool for real.
+in the same commit.
+
+How to read `--check`, measured on blankpad: it prints `RELINK` for **every** path the `zz`
+tier carries, even when the live link already points at the override — `rules.kdl`,
+`keybinds.kdl`, `misc.kdl`, `autostart.kdl` and `.zshrc` all did — because the walk
+processes the base package first and reports the intermediate owner change. A `RELINK` line
+therefore proves a pending change only when `readlink` shows the live target is *not*
+already the `zz-$HOST` file. `actions=0` is the only honest summary.
+## Law: never start a unit a session may already be running
+
+`sync` used to end with `systemctl --user enable --now` for every unit in `systemd-user/`
+whose `ExecStart` resolves. Measured on blankpad before one such run:
+
+|unit|`UnitFileState`|`ActiveState`|
+|---|---|---|
+|`live-sync.service`|`linked`|`inactive`|
+|`shelly-notifications.service`|`enabled`|`active`|
+|`swayidle-lock.service`|`enabled`|`inactive`|
+
+`swayidle-lock.service` was installed and **not running** — nothing started it, no swayidle
+process existed (`pgrep -c swayidle` = 0), and `autostart.kdl` does not launch one. A
+`deploy.sh` run would have armed it: monitors blanking and locking on the idle timer while
+the operator was mid-sentence. `live-sync.service` is `linked`, driven by its timer;
+`--now` forces a heartbeat commit at an arbitrary moment.
+
+Two rules follow. Install state must be read from the **printed state**, not the exit
+status — `is-enabled` exits 1 for `linked` exactly as for `disabled`, so exit status cannot
+tell "installed, driven by a timer" apart from "never installed". And a unit is started only
+in the latter case: a machine with a session on it has already decided what runs, while a
+fresh box — where everything reports `disabled` — still gets its units up. Both directions
+are pinned in `tests/deploy.bats` over a stub `systemctl`, because the real one on this box
+is exactly what must not be invoked from a test. Refs #44.
+
+## Law: the dconf dump holds preferences, not per-box state
+
+`dconf load /` writes every key in `dotfiles/dconf/dump.txt`, so the dump carries whatever
+box it was taken from. Comparing key by key against live state on blankpad found **six of
+24** keys that were not this box's, and not one of them was a preference:
+
+    [org/gnome/portal/filechooser/firefox] last-folder-path
+      repo: '/home/dank/Downloads'      live: '/home/blank/Downloads'
+    [org/gnome/nautilus/window-state]  initial-size, initial-size-file-chooser, maximized
+    [org/gnome/desktop/background]     picture-uri, picture-uri-dark
+      both: 'file:///home/dank/.config/background'
+
+A file-chooser memory, a window geometry, a wallpaper URI: application state that arrived
+with the dotfiles import. The last five did not appear as conflicts at all, because
+blankpad's **live** tree already held the same `/home/dank` values — an earlier deploy had
+written them here. A foreign value that agrees with live is invisible to any diff and still
+wrong. All six come out in #44; the two wallpaper URIs are also cleared on this box
+(`gsettings set org.gnome.desktop.background picture-uri ''`, and its `-dark` twin), because
+niri draws the wallpaper, noctalia owns it, and nothing reads a dead path.
+
+Compare **key by key**, not with a plain `diff`: `dconf load` writes only the keys present,
+so live-only keys survive and a diff overstates the damage in one direction and understates
+it in the other. Re-dump on the box whose settings are canonical (`dconf dump / >
+dotfiles/dconf/dump.txt`), then delete the state sections before committing — the census's
+*Never track: app state* class applies inside a tracked file, not just to whole directories.
+Refs #44.