docs(socketwatch): de-stale the 2b/2c prose - targeting reads the live map

[donislawdev]

What and why

Found during an engineering review of the concurrency layer. Chunks 2b/2c/2d landed in #38, so
ProcessTargeting has resolved against the live SocketWatcher map for a while now - but four
comments across three files still told the reader it was unwired ("NOT read by targeting yet -
that is 2c").

The interesting part is the failure mode, because it is not the one convention 5 usually catches.
Every one of those sentences was true when it was written. They carried an expiry date, and
nothing enforced it: check_notes.py deliberately does not check prose, so when 2c landed the
sentences quietly became lies sitting next to correct code. That is the exact shape of drift that
sends the next session down the wrong path - it reads "not wired yet" and re-derives, or worse,
re-implements.

Prose only. No behaviour change, no executable line touched.

• engine.py - the _socketwatch attribute comment and the _start_socketwatch docstring now
  point at _targeting_table() / _start_locked, where the poller-vs-watcher choice is actually
  made.
• socketwatch.py - the module docstring no longer claims the module is "in isolation ... NOT
  wired into the engine or targeting yet"; the lifecycle section header drops "in 2b".
• tests/test_socketwatch_wiring.py - kept the part that is still true (this file covers the
  plumbing only) and dropped the false framing, then named tests/test_targeting_socketwatch.py
  as the guard for the resolution contract. The sentence was wrong in its frame, not in its
  substance, so it was corrected rather than deleted.

Deliberately not touched: the SocketEvent comment saying remote_ip/remote_port are
"carried for the connection log later". Those fields are genuinely still unconsumed, and whether
they get used or cut is a separate decision - rewriting that sentence now would only produce prose
that decision will rewrite again.

Follow-up, on its own branch: a mechanical guard for expiring prose (PENDING(<id>) markers
checked against one list of open stage ids), since discipline alone produced four stale sites in a
single transition.

Checklist

• python -m pytest tests passes locally. (660 tests, 0 failures, on an elevated shell -
  so the two known non-admin failures are absent rather than excused. smoke_gui.py: OK.)
• New behaviour has tests (see tests/ for the style). - n/a: no new behaviour; the existing
  guards test_socketwatch*.py / test_targeting_socketwatch.py already cover the contract
  the prose now describes correctly.
• UI text goes through i18n keys, with both lang/en.json and lang/pl.json updated. -
  n/a: no UI text.
• User-facing changes noted in CHANGELOG.md; technical ones and new tests in
  CHANGELOG-INTERNAL.md, under [Unreleased]. - internal only (convention 39): nothing about
  this is visible to a tester.
• Commits follow Conventional Commits (type(scope): summary).
• No version bump - the owner closes a version via VERSION.txt.

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