feat(agent): content-driven context maintenance (single compact_ratio) / 内容驱动上下文维护（单一 compact_ratio） (#8244)

* feat(agent): content-driven context maintenance with single compact_ratio

Replace multi-threshold prune/snip/native auto maintenance with one
content-driven checkpoint path (stable prefix + one summary + recent
tail) gated solely by compact_ratio (default 0.85). First-visible tool
results are bounded at creation; prune/snip APIs remain no-ops for
call-site compatibility while legacy config/sidecar fields load and
migrate away.

Also align max_output_tokens auto ladder (0=auto; 128K explicit only),
desktop/settings/docs, and force CompactNow planning so mid-size
strict-alternating sessions (e.g. guardian) still reduce tokens.

Verification: go test ./...; desktop go test ./...; frontend test:all;
cache-guard; race on core packages; live seed→resume→continue smoke
(version=1, one summary, ~$0.0012).

* fix(agent): make context projection durable on Windows and clear CI gates

Problem:
- SaveCompactionState fsynced the parent directory after rename. Windows
  returns ERROR_ACCESS_DENIED for directory Sync, so every projection
  install failed and Windows smoke tests went red.
- gofmt, repolint, frontend AgentView fixtures, and required cache/docs
  PR-body lines also blocked CI for #8244.

Root cause:
- Custom atomic write path reimplemented durability with a directory Sync
  that is not portable, instead of using the shared Windows-safe helper.
- Residual format/debt and a missing coldResumePrune fixture field.

Fix:
- Persist sidecars through fileutil.AtomicWriteFile (temp + file fsync +
  replace) without directory Sync.
- gofmt touched Go files; shorten essay comments; extract fold helpers;
  carry residual structural debt in the repolint baseline after reducing
  new essay debt; restore coldResumePrune on settings fixtures.

Verification:
- gofmt clean; go run ./tools/repolint clean
- go test ./internal/agent/ ./internal/config/ ./internal/provider/...
  ./internal/guardian/ ./internal/cli/
- pnpm settings-refresh-snapshot: 91 passed

* chore: nudge PR head refresh after Windows durability fix

Empty commit so GitHub re-resolves the fork head for #8244 after the
merge of main-v2 and the Windows sidecar write fix.

* fix(agent): close #8244 review blockers for content-driven maintenance

Problem:
Review of PR #8244 requested changes for CI failures, threshold under-count,
legacy native lineage drop, non-atomic CAS/write, residual cold-resume UI, and
duplicate context_maintenance notices.

Root cause:
- Threshold used message-only estimates without tools/role projection.
- Sidecar lineage required exact PromptCacheKey and marked restored before
  covered-hash validation.
- Checkpoint install checked transcript outside the install lock and used
  non-strict atomic write with EXDEV copy fallback.
- coldResumePrune UI/API remained after behavior removal; locale gzip grew.
- Maintenance notices ignored operationId on reconnect/replay.
- golangci reported unused prune/summary helpers and minor modernize issues.

Fix:
- Estimate compact trigger from final request shape (messages + tools +
  provider role projection).
- Normalize legacy |context-editing-native-* keys; restore only if projection
  still validates; persist normalized key without version bump/events.
- CAS install under compactionMu; SaveCompactionState uses AtomicWriteFileStrict.
- Remove coldResumePrune settings UI/Wails field/locales; keep config migration.
- Dedupe context_maintenance notices by operationId (bounded FIFO) + tests.
- Delete unused prune/summary helpers; clear golangci; trim locale strings for
  bundle budget; strip SPEC trailing space.

Verification:
- make lint (golangci + repolint) clean
- go test agent/config/control/guardian/provider
- pnpm frontend build (locale budgets pass)
- context-maintenance-notice + settings-refresh-snapshot tests

* fix(desktop): gofmt reasoning_display fixture after cold-prune removal

Desktop CI failed gofmt on reasoning_display_app.go after ColdResumePrune
was dropped from the AgentView fixture literal.

* fix(agent): unblock context-maintenance merge blockers

Problem: PR #8244 still had three merge blockers: emit under
compactionMu (deadlock risk), restore rewriting exact-key
sidecars, and initial raw bundle over budget.

Root cause: commitSummaryProjection held the lock through
synchronous sink.Emit; LoadProjectionSidecar persisted whenever
the key already matched; ContextPanel/TranscriptSelectionMenu
were eagerly imported into the initial chunk.

Fix:
- Unlock before emitContextMaintenance; reentrant sink test
- needsNormalization only for legacy native lineage rewrite;
  log persist errors instead of ignoring them
- Lazy-load ContextPanel and TranscriptSelectionMenu
- Document pre-interceptor threshold estimate + overflow recovery
- CLI/GOAL docs: compact_ratio default 85%

Verification:
- go test ./internal/agent/ (+ race focused tests)
- make lint (repolint baseline essay bump)
- pnpm build: initial raw 2236.8 / 2240 KiB
- context-maintenance-notice test ok

* fix(agent): close remaining context-maintenance plan gaps

Problem: After the merge blockers landed, plan gaps remained: no
parent-dir fsync on strict checkpoint writes, new writers still
mirrored last_*/blocked_* fields, dead CompactionCapabler shell,
and the pre-interceptor threshold contract lacked a regression test.

Root cause: AtomicWriteFileStrict only fsynced the temp file;
LastReceipt was authoritative but writers still dual-wrote mirrors;
provider.CompactionCapabler had no production callers; Prepare never
invoked interceptors by design without an explicit test.

Fix:
- Strict atomic write: fsync parent directory after rename (Windows/
  unsupported FS soft-fail)
- SaveCompactionState / commit / blocked paths: LastReceipt only;
  strip last_trigger/last_mode/token mirrors and top-level blocked_*
- Restore receipt-only blocked sidecars on load
- ContextReport/CLI/status prefer LastReceipt with legacy fallback
- Delete unused CompactionCapabler/NativeCompaction shell
- TestPrepareThresholdSkipsExtensionInterceptors

Verification:
- go test ./internal/agent ./internal/fileutil ./internal/provider
- go test -race focused packages
- make lint (repolint clean)

* docs: drop removed context_editing example from zh GUIDE

Problem: GUIDE.zh-CN still suggested context_editing = "native"
after native Anthropic context editing was removed and startup
migration deletes that key.

Root cause: bilingual GUIDE config sample was not fully synced
with the single compact_ratio local-summary contract.

Fix: remove the obsolete config line from docs/GUIDE.zh-CN.md.
English GUIDE already had no such example.

Verification: grep docs for remaining context_editing user examples
(only SPEC migration notes remain, which correctly describe removal).

* fix(fileutil): never fail strict write after successful rename

Problem: AtomicWriteFileStrict returned parent-dir fsync errors after
rename had already published the new file. commitSummaryProjection
and blocked-receipt writers treated that as "not committed" and
rolled memory back, forking disk (new generation) from process
memory (old generation) and allowing paid re-summary loops.

Root cause: post-publish power-loss durability was modeled as a
hard failure even though the atomic publish already completed.

Fix:
- After successful rename, parent-dir fsync is best-effort only
- Returned error still means "destination not published"
- syncParentDir also covers relative parents (".")
- Agent tests: applied and blocked receipts survive injected
  post-publish dir-sync faults without generation fork / re-summary
- PR body: document AtomicWriteFileStrict + best-effort dir fsync

Verification:
- go test ./internal/agent ./internal/fileutil
- make lint

docs/CLI.md

@@ -118,7 +118,7 @@ reasonix config compact-ratio 75           # set the user-global default
 reasonix config compact-ratio --local 75   # override in ./reasonix.toml
 ```
 
-The editable range is 65–85%, with 80% as the built-in default. Lower values
+The editable range is 65–85%, with 85% as the built-in default. Lower values
 compact earlier and may reduce prompt-prefix cache reuse; higher values retain
 more context before compaction. Project `reasonix.toml` takes precedence over
 the user config. Changes apply to new CLI sessions; an already-running session