fix(deploy): report what enable actually did, and arm the tier's timers

Two lies in the unit loop, both reported as success:

- `systemctl --user enable live-sync.service` fails on every deploy — the file has
  no [Install] section, because live-sync.timer is what arms it. The result was
  swallowed by `|| true` and the tool printed ENABLE anyway, so the line an
  operator reads after a rebuild was false on every box, on the repo's own
  heartbeat. The [Install] section is readable from the file being deployed, so
  the tool now checks it and prints INERT with the reason instead of making a
  call that cannot succeed; a real enable failure prints INERT too.
- The loop walked *.service only. live-sync.timer was never enabled by anything,
  so a rebuilt box got the heartbeat and no schedule for it. Timers are walked
  now; a timer has no ExecStart, so the "does this unit belong on this box" test
  runs against the service it activates.

The systemctl stub models systemd's refusal (no [Install] section -> non-zero),
which is what makes the new tests red against the old loop; both new tests were
run red first, and the five existing unit tests still pin #44's semantics.

Refs #60

omp-docs/tools/dotfiles-deploy.md

@@ -25,10 +25,15 @@ 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`; 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.
+Two package shapes are not symlinks. `dconf/dump.txt` is loaded with `dconf load /`. The
+`systemd-user` tier gets `daemon-reload`, then **every `*.service` and `*.timer` whose start
+command resolves on this box** is enabled — a timer is the schedule that makes a oneshot service
+run at all, and it carries no `ExecStart` of its own, so the belonging test is applied to the
+service it activates. A unit is **started** (`--now`) only when systemd reports it as nothing-yet
+(`""`/`disabled`), and never when its binary is absent here, so a unit belonging to another box
+stays inert instead of crash-looping. Three outcomes are printed, and each says what actually
+happened: `ENABLE` only when `systemctl enable` returned success, `INERT` when it could not or did
+not, `SKIP` when the unit is foreign. Refs #44, #60.
 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*.
 
@@ -167,6 +172,15 @@ fresh box — where everything reports `disabled` — still gets its units up. B
 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.
 
+**A third state exists, and it is not an error.** A unit file with no `[Install]` section cannot be
+enabled at all — `systemctl --user enable` answers with a non-zero exit and a paragraph about
+missing `WantedBy`. `live-sync.service` is one on purpose: `live-sync.timer` pulls it in, which is
+also why systemd reports it as `linked`. Until 2026-10-21 the deploy swallowed that failure and
+printed `ENABLE` anyway, so the line an operator reads to learn what a rebuild armed was false on
+every box, on the repo's own heartbeat. The section is readable from the file being deployed, so
+the tool checks it and prints `INERT …(no [Install] section — another unit arms it, enable cannot)`
+without making the call. Refs #60.
+
 ## Law: expand systemd specifiers before calling a unit foreign
 
 `ExecStart=%h/.omp/scripts/live-sync.sh` is valid systemd and meaningless to a shell. The