fix(compact): size the compaction e2e to actually cross threshold; sync stale docs (CBR-007)

The compaction e2e never exercised compaction: its window/fixture combo
(contextWindow 8000, thresholdRatio 0.5 → threshold 4000; four small files)
peaked at ~1389 estimated tokens, so compactIfNeeded declined every pre-step
and compact/start never landed. Shrink the window (contextWindow 2400 →
threshold 1200; retainTokens 500 + summarizationMaxTokens 300 = 800 < 1200,
convergence holds) and grow the fixture to six files so a couple of bash steps
reliably cross the threshold. Verified compaction fires and the suite passes
across repeated real-API runs.

Sync docs left stale by the landed compaction work: list compaction.e2e.ts and
keyless-smoke.e2e.ts in the coding-agent README (and fix the wrong "Both
self-skip" count), add compaction to the examples with-key inventory, and
replace the hypothetical compaction/marker / "future plugin" naming in the
session README, session types JSDoc, and the core-data-structures catalog with
the real compact/start, compact/summary, compact/end events.

examples/coding-agent/README.md

@@ -48,5 +48,6 @@ This example is a thin leaf `cordis.yml`: it picks the swappable backends and lo
 - `tests/full-loop.e2e.ts` — the canary: real model runs `echo e2e-ok` through the real bash tool; asserts `tool/call`/`tool/result` session events and the final answer.
 - `tests/coding-task.e2e.ts` — the swebench-style smoke: a temp dir holds `add.js` (with `a - b` where `a + b` belongs) and a failing `add.test.js`; the agent must fix the bug and verify. The test re-runs `node add.test.js` ITSELF and inspects the files — agent claims are not trusted.
 - `tests/resume.e2e.ts` — durable continuity across processes: run 1 tells the real model a secret code and persists the turn to a temp JSONL root, then the whole context is disposed; run 2 is a fresh context over the same root that RESUMES the session id and asks the model to recall the code. The recall can only come from the rehydrated log.
+- `tests/compaction.e2e.ts` — the compaction smoke: a real multi-step bash task runs with a deliberately tiny context window so the auto-compaction listener fires MID-SESSION. Verifies the WORLD — a `compact/start…end` pair landed in the real log, the surface shrank (a replace node shadowed older nodes), and the agent still produced a correct final answer after compaction.
 
-Both self-skip without `DEEPSEEK_API_KEY`.
+All four self-skip without `DEEPSEEK_API_KEY`. The keyless boot smoke is `tests/keyless-smoke.e2e.ts` (boots the full real tree with a dummy key and no prompt, so no model call), which runs in the default e2e gate.