feat(scripts): tools to destroy documentation, not preserve it

Point-of-use enforcement needs hands, not advice:

- `destroy-vault.py` — moves the pages on a kill list to `.AGENTTRASH/` and then
  deletes every reference to them from the survivors, including the whole line
  when the dead link was the line's only content. Stems are seeded from the trash
  so the pass is re-runnable; `pathlib.Path.stem` is NOT used to compare link
  targets, because it strips the real suffix off names like `sd.cpp`.
- `axe-measurements.py` — deletes bench/throughput ledger sections and rate rows,
  blanks any table cell that reports a rate, and folds Eras older than the current
  one into a single row that says the numbers were destroyed and that rollback is
  a commit. Never touches a shape number or a Law/Wire/Rollback section.
- `repair-damage.py` — fixes the two artifacts those passes can leave (a list
  marker that lost its space, a table separator left without its header).
- `restore-punctuation.py` — restores a line whose only difference from HEAD is
  stripped trailing punctuation. Written after `repair-damage.py`'s first version
  matched every wrapped prose line ending in a comma and deleted 660 of them: the
  rule is now `… see .` only, and the incident is recorded in its docstring.
- `gen-vault-index.py` — never walks into `.AGENTTRASH/`, and sweeps rows whose
  page cell is empty (a description left nameless by a destruction).

Full suite: 451 tests pass.

scripts/gen-vault-index.py

@@ -107,6 +107,11 @@ def sync_subindex(index: pathlib.Path, vault: pathlib.Path):
     lines = index.read_text().split("\n")
     out, dropped, refreshed = [], 0, 0
     for line in lines:
+        # A row whose first cell is empty is a description with no page: the link
+        # was deleted when the page was destroyed, so the row is a dead promise.
+        if re.match(r"^\|\s*\|", line.strip()):
+            dropped += 1
+            continue
         for pat, wrap in ((ROW, "| [[{}]] |{} {} |"), (BULLET, "- [[{}]] — {}")):
             m = pat.match(line)
             if not m:
@@ -191,7 +196,7 @@ def main(argv):
     index.write_text("\n".join(out) + "\n")
     touched = 0
     for sub in sorted(vault.rglob("index.md")):
-        if sub == index:
+        if sub == index or ".AGENTTRASH" in str(sub):
             continue
         dropped, refreshed, added = sync_subindex(sub, vault)
         if dropped or refreshed or added: