phase0: exit criteria met — tokei +10.4% median [8.5%, 12.0%] verified

Attempt 4 (phase0-tokei-002, class 3, ACCEPTED — first auto-accept):
every file was read through encoding_rs_io's DecodeReaderBytes via
generic read_to_end, which zero-fills every grown buffer chunk (~221MB
memset/run, 8.5% of Ir) and grows without a size hint. Patch: fs::read
with a BOM-gated fallback to the identical decode path (a UTF-8-BOM
file transcodes invalid sequences, so the fallback is required for
equivalence). Gates: golden byte-identical; differential fuzz old-vs-
new binaries 4,332 iterations (BOM grid, invalid UTF-8, binary junk,
randomized) zero divergence; 250 upstream tests green; ASan+LSan clean
with ASan-run output hashing to golden. Bench: +9.9% [8.0%, 12.7%].

Attempt 5 (phase0-tokei-003, ship tree, ACCEPTED): stacks fat LTO+cgu=1
(real +1.6% standalone but under threshold, phase0-tokei-001) on the
accepted patch; benched as a whole vs pristine: +10.4% [8.5%, 12.0%].
Median clears the Phase 0 exit bar; CI lower bound 8.5%.

Case study written (results/phase0/case-study-tokei.md), ledger at 5
attempts, CLAUDE.md phase line moved to Phase 1, next hypotheses
logged (tokei class-5 byte-skip table; comrak class-3 arena).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2

CLAUDE.md

@@ -32,7 +32,7 @@ Full engineering spec: `SPEC.md`. Read it before starting any phase.
 
 ## Current phase
 
-**Phase 0 — manual dry run.** (Update this line as phases complete; exit criteria in SPEC.md §5.)
+**Phase 0 complete → Phase 1 — trust layer.** Phase 0 exit met 2026-07-06: verified +10.4% median win on tokei (95% CI [+8.5%, +12.0%], ledger `phase0-tokei-003`) + two case studies in `results/phase0/`. Phase 1 gaps to close: dedicated no-net bench containers, perf-based profiling, automated A/A + regression-injection calibration, diff-test orchestration, agent↔harness IPC. (Update this line as phases complete; exit criteria in SPEC.md §5.)
 
 ## Commands