[ADR-021] Memory recall + rerank pipeline (cluster-18)

[ohdearquant]

Summary

• F107: handle_remember now always writes memory_type to note properties (defaults to episodic when omitted)
• F108: importance and decay_factor validated on input — importance must be in [0, 1], decay_factor must be >= 0
• F109: source_id UUID validated on input; invalid UUIDs return RuntimeError::InvalidInput rather than silently being ignored
• F111: collect_recall_candidates FTS5 query now scopes to SubstrateKind::Note via TextFilter.kinds; memory-kind post-filter in load_memory_candidate_notes remains as the second gate per ADR-021 §6 bounded-over-fetch semantics
• F110: DecayModel::Exponential corrected from half-life-derived constant to salience * exp(-decay_factor * age_days) using the note's own decay_factor field
• F222 (partial): recall.rerank subhandler registered in MEMORY_HANDLERS (ADR-033 §2); v1 implementation is a pass-through stub — main handle_recall does not invoke it yet (see memory: wire recall.rerank into main recall path (ADR-033 §6) #375)
• ADR-033 §4 objectives (partial): Added DecayAwareImportanceObjective, TemporalRecencyObjective, and RerankerObjective to khive-runtime/src/objectives.rs; added NoteCandidate pre-computed signals struct; RrfFusionObjective gains a second impl Objective<NoteCandidate> trait impl — these are not yet wired into the pack recall path (see memory: replace inline compute_score with ComposePipeline/NoteCandidate from objectives.rs (ADR-033 §4) #378)
• RecallConfig: Added reranker_weights, reranker_params, fallback_during_migration fields (declared/defaulted; not yet consumed by handlers — see memory: implement or remove scaffolded RecallConfig fields (reranker_params, fallback_during_migration) #376)

Codex round-1 post-rebase: finding closure

Finding	Severity	Status	Follow-up
F107	CRIT	closed	—
F108	CRIT	closed	—
F109	CRIT	closed	—
F110	CRIT	closed	—
F111	CRIT	closed	—
F175	MAJ	closed	—
F185	MAJ	closed	—
F112	MAJ	not addressed	deferred
F174	MAJ	not addressed	#377
F187	MAJ	not addressed	#377
F190	MIN	not addressed	deferred
F184	CRIT	partial	#375
F186/F223	MAJ	partial	#376
F230	MAJ	partial	#376
F188	MAJ	partial	#378
F189	MAJ	partial	#375 #378
F222	CRIT	partial	#375

7 fully closed / 7 partial / 4 not addressed of 18 source findings.

Merge-base fix

This branch was rebased onto origin/integration/v1-adr-alignment (SHA c567f4d) after the
codex round-1 review found it would have silently reverted cluster-15 (GTD schema + lifecycle
audit, 304 test lines) and cluster-24 (ADR-015 migration ledger amendment). The rebase preserved
all c18 additions; conflict resolution kept BOTH the new memory-pack objective re-exports AND the
existing NoteKindSpec/PackSchemaPlan/SchemaPlan/validation re-exports from c11/c15.

Test plan

• cargo fmt --all -- --check passes
• cargo clippy --workspace --all-targets -- -D warnings passes (0 warnings)
• cargo test --workspace passes (all suites green)
• make ci passes including smoke tests

Files changed (c18 commit only)

File	Change
khive-pack-memory/src/config.rs	ADR-021 §5 Exponential decay formula; new RecallConfig fields; validation
khive-pack-memory/src/handlers.rs	F107/F108/F109/F111 fixes; handle_recall_rerank (F222)
khive-pack-memory/src/lib.rs	Register recall.rerank subhandler
khive-pack-memory/tests/integration.rs	5 new integration tests; updated existing tests for new semantics
khive-runtime/src/objectives.rs	NoteCandidate, 3 new Objectives, dual RrfFusionObjective impl
khive-runtime/src/lib.rs	Re-export new objective types

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