feat(context): aggressive token-engine — adaptive intensity, redundancy cache, summarize fallback

[claudioemmanuel]

Summary

PR1 of two implementing the squeez token-optimizer roadmap. Adds the context optimization layer (src/context/) — a minimally-invasive engine that sits between filter::compress and wrap.rs and attacks three sources of token waste squeez previously ignored.

• Adaptive intensity — bash header now reports the active level (Lite/Full/Ultra) and per-handler limits (max_lines, dedup_min, git_diff_max, docker_logs_max, find_max, summarize_threshold) automatically scale as cumulative session usage approaches the compact_threshold budget. Floors enforced so we never reduce to zero.
• Cross-call redundancy cache — the same compressed output within the last 8 calls is collapsed to a single reference line: [squeez: identical to <hash> at bash#<n> — re-run with --no-squeez]. Length-equality guarded against FNV-1a collisions; tiny outputs (<5 lines) skipped.
• Summarize fallback — raw outputs over 500 lines (configurable) are replaced with a dense ≤40-line summary (top errors, top files, test summary, last 20 lines verbatim) instead of running through per-handler truncation.
• SessionContext persists at sessions/context.json next to current.json with bounded ring buffers (32 calls, 256 files, 128 errors, 64 git refs). Hand-rolled flat-array JSON — no serde, zero new dependencies (still just libc on Unix).
• Cross-call hint — cat/head/tail/less/more/bat of a file already in context emits a one-line hint without blocking execution.

All new behavior is opt-out via four new config keys (adaptive_intensity, context_cache_enabled, redundancy_cache_enabled, summarize_threshold_lines). Existing handlers and strategies are untouched; the wrap.rs diff is ~30 lines.

Changes

• New src/context/ module: intensity.rs, cache.rs, redundancy.rs, summarize.rs, hash.rs (FNV-1a 64), mod.rs
• src/commands/wrap.rs: pre/post-pass insertion + [adaptive: <Level>] header tag
• src/config.rs: 4 new fields with defaults + INI parser arms
• src/json_util.rs: extract_u64_array, u64_array, usize_array helpers
• bench/fixtures/: summarize_huge.txt, intensity_budget80.txt, context_crosscall_{1,2,3}.txt
• bench/run_context.sh: end-to-end wrap-mode bench (3 scenarios)
• bench/run.sh: skips context_crosscall_* (handled by run_context.sh)
• .github/workflows/ci.yml: runs bench/run_context.sh after bench/run.sh
• README.md: documents the four new config keys + intensity model

Test plan

• cargo test — 167 passing (was 132)
• cargo build --release — clean
• bench/run.sh — 12/12 fixtures pass (incl. new summarize_huge 100% reduction, intensity_budget80 99% reduction)
• bench/run_context.sh — 3/3 scenarios pass:
  • summarize_huge triggers summary header, output ≤60 lines
  • intensity_budget80 with seeded current.json shows [adaptive: Ultra]
  • context_crosscall_{2,3} emit redundancy reference lines after _1
• CI workflow updated to run both bench scripts

Risks & mitigations

Risk	Mitigation
FNV-1a 64 collision	exact-length guard + scoped to 32-entry ring per session
Cross-call dedup hides important re-output	RECENT_WINDOW=8; opt-out via redundancy_cache_enabled=false
Adaptive intensity surprises users	header always shows [adaptive: <Level>]
Zero new deps	confirmed: only libc (Unix-only) in Cargo.toml

PR2 (memory compressor + caveman persona + squeez update + track-result hook) will follow on top of this branch.

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