bugfix(timeline): anchor decision-date regex to bullet end, not first match

[CryptoJones]

_decision_events parsed lines like

• Migrate by (2024-12-31) for compliance (2026-05-20)
  with an unanchored regex \((\d{4}-\d{2}-\d{2})\). re.search returns
  the FIRST match — so the user's deadline date (2024-12-31) was used as
  the decision's recording date, instead of the trailing stamp
  (2026-05-20) that record_decision/_decisions_md actually emit.

socrates timeline would then place the decision at the wrong point
in the chronological feed, breaking the whole "what happened on this
project in order?" premise.

Fix: try an end-anchored regex first
((\d{4}-\d{2}-\d{2}))*{0,2}\s*$
which matches the canonical bullet shape (with or without the bold
markers). Fall back to the unanchored regex for legacy bullets that
don't end in )**. The stripped-from-content regex is also anchored,
so a user-typed date in the body is preserved in the rendered title.

Tests added (2):

• bullet with user-typed date BEFORE the recording stamp → uses the
  trailing stamp, and the body-date is preserved in the title.
• bullet with NO trailing )** → fallback regex still picks up
  the single in-line date.

149/149 tests pass; ruff + mypy clean.

Self-review caveat: partial fix. The unanchored FALLBACK regex (for legacy non-canonical bullets) still has the original bug — for those, the FIRST date in the line still wins. Only the canonical )** -terminated bullets get the fix. Acceptable because all NEW bullets from record_decision use the canonical form.