fix: remove fatal per-turn compaction cap

[realsigridjin]

Summary

• Allow required compaction beyond the former per-turn soft cap.
• Retain the absolute hard cap of 10 and report it accurately.
• Cover accepted, ineffective, route-guard, and degradation-recovery paths.

Validation

• npm --prefix packages/coding-agent test -- test/compaction (52 files, 392 tests)
• npm run build

---

Summary by cubic

Removed the per-turn compaction cap so required compactions can continue within a turn. Compaction now only stops at the absolute session cap (10), preventing premature turn termination.

• Bug Fixes
  • Enforce only the absolute cap of 10 via shouldRejectByCap; removed soft-cap checks.
  • Updated logs and rejection text to “absolute compaction cap” and count acceptedAbsolute.
  • Fixed route guards to admit compaction across turn boundaries and after degradation recovery until the hard cap.
  • Updated tests for absolute-cap behavior (accepted, ineffective, route-guard, and recovery paths).

^{Written for commit bb08d0e. Summary will update on new commits.}

[code-yeongyu]

Thanks @realsigridjin (Sigrid) — the intent here was right: the per-turn soft cap made required compactions fatal mid-turn, and removing it in favor of the absolute session cap is exactly what landed.

This PR could not pass the Changelog gate (runtime source changed without a CHANGELOG.md entry) and also missed the fork's changes.md/AGENTS.md/QA-evidence gates, so we reworked the same policy change end to end in #731:

• per-turn soft cap removed; admission bounded only by the absolute session cap (10) + circuit breaker
• rejection message corrected to "absolute compaction cap reached for this session" (cause id kept for extension-API stability)
• CHANGELOG.md [Unreleased] entry, fork-tracker changes.md entries, AGENTS.md/fixture doc sync
• committed senpi-qa RPC scenario (compaction-absolute-cap-qa.mjs): 10 accepted compactions in one session, non-fatal absolute-cap rejection, baseline on old code showing the misleading per-turn wording

#731 is merged with full CI green, so closing this one in its favor. Credit for the diagnosis and direction stays with this PR.