feat(docs-audit): anchor a docs page on the CLI command phrase a change implements (#9290)

Adds a fourth anchor kind, `command`, to the docs-drift derivation: when a changed
file sits under an oclif package's `src/commands/**`, the phrase `os <topic> <name>`
is derived from its path and matched against the hand-written corpus.

The registry this needs already exists as the oclif filesystem convention (topic =
directory, command = filename), so the derivation reads the path — no curated table
beside it to drift.

The lowercase shape guard is untouched for bare tokens. `resync` alone is exactly
the shape it exists to drop; `os meta resync` is a multi-word phrase that is
distinctive by construction, so the new kind is admitted beside the guard via
PHRASE_ANCHOR_KINDS rather than through it. Command phrases still face the
corpus-share guard.

Measured: 07ad424 goes from 0 matched pages to the page naming the command.


Claude-Session: https://claude.ai/code/session_01XqDQYVU5smx29ts9pAErja

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-steve