docs: reflect the trajectory measurement back onto the approved spec

learning-harness divides cleanly. The measurement layer stands and is worth
more than before -- it is what made a $0.23 experiment able to answer 'is
our own instability structural?'. What was answering the wrong question:
Req 3.5's K (an ensemble of distinct search procedures, not a repeated
measurement), Req 8.2's noise floor (it measures how often an unconstrained
search reaches the sink, so the regression budget grows with the search's own
wandering), Req 9.5's acceptance rule, and the sign test added this session.

And the highest-leverage change in either spec turns out not to be a prompt,
a lever or an optimizer: stop asking the model to locate the sink. 555 grep
calls against 71 entry_points, while the CST and the entry-point mapper
already know where the sinks are.

Limits stated in the brief: twelve pairs, one family, one model; the
high-similarity bucket is two run pairs and its 0% is decoration.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG

.kiro/specs/learning-harness/tasks.md

@@ -246,3 +246,4 @@
   - **`ousast pairs --hunter` crashed in its documented form.** The K floor landed with `--k-runs` still defaulting to 1, so the flag's absence raised `ValueError` from inside `evaluate_catalog`. The default is `None` (three), and a breach exits naming the flag. The covering test always passed `--k-runs 4`, which is why nothing noticed.
   - **28 rows resolved a span on the vulnerable side and none on the fixed side** (12% of the corpus), so every fixed-side finding read as outside the labeled function and the pair scored as silence whatever the detector said — the same flattering direction as the range defect, one-seventh the size. `fix_function` reached only the harvester; it now reaches the catalog and `PairCase`, `_spans` uses it for the fixed side, and the catalog generator derives it from the fixed excerpt itself for the 25 vibe-py trap rows that never declared one. A row that still resolves no fixed-side span reports `unresolved_label:fixed` instead of scoring silent. Measured after: **0 rows**.
   - Suggestions applied: one spelling per corpus fact everywhere (`PairCase.unscorable` verbatim, no invented prefix); leave-one-out records non-teachers withheld for tier or an unscorable reason, not only holdout refusals; the hygiene test asserts the declared twins still hash equal, so a declaration that stopped being true would not be invisible; `is_post_cutoff` refuses a cutoff coarser than a day, which was the one over-claim path that existed, and month precision is pinned; `UNSCORABLE_REASONS` covers the whole vocabulary rather than `identical_twin` alone; the zero-run score carries its date; `_pairs_named_by` filters by substring before the regex.
+- Carry-forward, measured 2026-09-06 after group 4 (`benchmarks/measurements/2026-09-06-trajectory-divergence.json`): **the K-run numbers this spec publishes are ensemble votes, not repeated measurements.** Across 120 runs of the injection family at temperature 0 with thinking disabled there was not one repeated tool-call trajectory, and outcome disagreement tracks trajectory divergence (30.9% at low similarity, 4.2% at mid). Consequences for anyone reading these numbers: Req 3.5's K is an ensemble over distinct search procedures; Req 8.2's noise floor measures how often an unconstrained search reaches the sink rather than the detector's uncertainty, so Req 9.5's regression budget grows with the search's own wandering; and the instability is entirely one-sided — every pair produced a single finding set on the fixed side, so specificity is solid and recall carries the caveat. `.kiro/specs/detector-optimizer/brief.md` proposes the repair, and it is a program change rather than a prompt change.