chore(p0): drop never-enabled hunter tools, test-only functions and receiver delivery

Off every active line (PATHFINDER-2026-10-13/03-unified-proposal.md, cuts).
Deleted: the four hunter tools no caller enables (read_definition,
entry_points, flows, obligations) with their schemas and dispatch, the dead
mapping branch of find_refs; 20 functions whose only caller was one test
(mapping task records, compute_ranking_metrics, build_quick_hunter_prompt,
validate_evidence_transition, should_fuse, harness processors,
rank_targets_with_model, model/report slice rendering, taxonomy
hierarchical/related, config_value.verdict, taint.verdict, roles.load_roles,
features.language_of and build_for_scan, folds.leave_one_*,
features.recorded_case, search BatchExecutor and the three __main__ shims,
delivery.put_input); the receiver delivery mode of the plane. push_inputs.py
moved to benchmarks/push. memory.purge stays: the live-S3 test cleanup uses
it. Net: 2,730 lines deleted, 207 added. 473 targeted tests passed; 3,282
tests collect. breadth.toml records the removals.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

docs/memory-and-detection.md

@@ -26,11 +26,7 @@ flowchart TD
     op -- "otherwise" --> adv["ADVISORY"]
 ```
 
-These decisions are meant for changed code. `learn/features.py` builds feature records in two ways:
-
-- for a whole-repository scan;
-- for a base..head delta (`build_for_scan` with `Delta`). This is the same delta `ousast pre-push` checks.
-
+The plane task uses `learn/features.py` to build candidate feature records from delivered artifacts.
 Integration into scan and pre-push is still ahead.
 
 ## 1. Instruments produce signals, not verdicts