QA Results: Feedback Loop UX

Test Execution Summary

Suite	Command	Result	Details
Feedback unit tests	`cargo test --lib -- feedback`	PASS	21 passed, 0 failed
Integration tests	`cargo test --test p1_feedback_loop`	PASS	10 passed, 0 failed
Full lib suite	`cargo test --lib`	PASS	1352 passed, 0 failed, 0 ignored
Format check	`cargo fmt --check`	PASS (feedback files)	Pre-existing diffs in unrelated files (metrics/histogram.rs, executor/mod.rs, etc.)
Clippy check	`cargo clippy -- -D warnings`	PASS (feedback files)	Pre-existing warnings in experiment/mod.rs, ranking/reason.rs only

Test	Status
`submit_like_updates_liked_bitmap`	PASS
`submit_unlike_removes_from_liked_bitmap`	PASS
`submit_hide_adds_hard_neg_and_hidden`	PASS
`submit_unhide_removes_hard_neg_and_hidden`	PASS
`submit_mute_creator_blocks_creator`	PASS
`submit_unmute_creator_unblocks_creator`	PASS
`submit_dislike_adds_hard_neg`	PASS
`submit_undo_dislike_removes_hard_neg`	PASS
`submit_save_and_unsave`	PASS
`submit_not_interested_marks_seen`	PASS
`skip_escalation_to_hard_neg`	PASS
`skip_below_threshold_no_hard_neg`	PASS
`feedback_state_after_like`	PASS
`feedback_state_after_hide`	PASS
`feedback_state_after_dislike`	PASS
`feedback_state_after_mute_creator`	PASS
`feedback_state_default_all_false`	PASS
`unlike_on_never_liked_is_noop`	PASS
`unhide_on_never_hidden_writes_signal_ok`	PASS
`like_then_dislike_both_states_coexist`	PASS
`submit_feedback_with_write_item`	PASS

Test	Status
`like_and_unlike_roundtrip`	PASS
`hide_and_unhide_roundtrip`	PASS
`dislike_and_undo_dislike_roundtrip`	PASS
`mute_and_unmute_creator`	PASS
`save_and_unsave_roundtrip`	PASS
`skip_escalation_at_threshold`	PASS
`feedback_state_default_for_unknown_pair`	PASS
`multiple_users_independent_feedback`	PASS
`negative_preference_update_on_dislike`	PASS
`combined_actions_feedback_state`	PASS

Full lib test suite: 1352 passed, 0 failed. No regressions introduced.

Double-like idempotency: no panic, no double-count
Unlike on never-liked item: no-op (no error)
Unhide on never-hidden item: writes signal, no error
Like then Dislike coexist: both states true, hard-neg exclusion takes precedence
Multi-user independence: User A's feedback does not affect User B

Pre-existing cargo fmt diffs exist in files unrelated to this feature (metrics/histogram.rs, executor/mod.rs, search pipeline, reason.rs, test files). These are from concurrent feature work and do not affect feedback functionality.
Pre-existing clippy warnings exist in experiment/mod.rs and ranking/reason.rs. These are from concurrent feature work (p1-briefing-ux-reason-labels, pg1-instrumented-metrics).

PASSED. All 31 tests (21 unit + 10 integration) pass. Full regression suite (1352 lib tests) clean. Feature is ready for merge.