fix: preserve growth baseline when nothingToCompress

[ranxianglei]

Problem

When the growth threshold was met (nudgeAllowed=true) but there was nothing to compress (nothingToCompress=true), inject.ts:368 reset lastPerMessageNudgeTokens = currentTokens. This "ate" accumulated growth, creating a feedback loop in short sessions (e.g., subagent sessions):

1. Context grows → growth ≥ 50K → nudgeAllowed = true
2. But nothingToCompress = true (all ranges protected by preserveRecentMessages: 20) → shouldInject = false
3. Baseline reset to current context → growth forgotten
4. Need another 50K growth before next attempt
5. Cycle repeats → model NEVER sees a nudge

Observed in ses_0604a0a1affebNnnFMo5KiM7GD: 31 API calls, context grew 719→142K, baseline ended at 132K (near peak).

Fix

Remove lastPerMessageNudgeTokens = currentTokens from the nothingToCompress path. Only clear lastNudgeShownTokens. Growth baseline is preserved so it accumulates until there IS something to compress.

The baseline is still correctly reset via the compress-detection path (inject.ts:108-156) when the model actually compresses.

Files

• lib/messages/inject/inject.ts — 1 line removed from nothingToCompress block
• tests/baseline-reset.test.ts — 3 regression tests
• tests/inject.test.ts — 3 existing tests updated for new behavior
• devlog/2026-07-27_fix-baseline-reset/ — REQ.md + WORKLOG.md

Test Results

• 922 tests pass (919 existing + 3 new), 0 failures
• typecheck ✅, build ✅