feat(core): O-13 PR4 ArenaLifecycleCoordinatorV1 unified lifecycle + zero-alloc gate

[lemone112]

Summary

Implements the ArenaLifecycleCoordinatorV1 per IMPL-SPEC-o13-pr4-lifecycle-coordinator.md. Coordinates lifecycle transitions across observation, field raster, and report arena pools with atomic reset, release, and generation tracking.

Replaces closed PR #632 with updated branch state rebased on current main.

Types Added

• ArenaGenerationV1 — monotonic generation counter for slot validity detection
• ArenaLifecycleCoordinatorV1 — coordinates reset_all / release_all_slots across all three pool types
• ArenaRebindErrorV1 — typed error enum for partial-failure detection during schema rebind

Pool Extensions

• ObservationArenaPoolV1: added release_all(), high_water_mark(), generation field in backing
• FieldRasterArenaPoolV1: added reset_extent(), release_all(), high_water_mark(), generation field in backing
• ReportArenaPoolV1: added reset(), release_all(), generation field in backing

Tests (13 total)

• 5 unit tests: coordinator construction, generation increment, capacity preservation, unique ownership after release, staleness detection
• 5 integration tests: zero-allocation gate (10K iterations), high-water mark bounds, atomic schema rebind success, partial failure detectability, byte identity preservation
• 3 property tests: generation monotonicity, slot count invariant, zero-alloc closure per transition type

Gate Results

• cargo check --workspace: PASS
• cargo test --workspace: PASS (all tests green)
• cargo clippy --workspace --all-targets -- -D warnings: CLEAN
• cargo fmt --check: CLEAN
• RUSTDOCFLAGS=-D warnings cargo doc --workspace --no-deps: PASS
• verify_clean_set_receipt.py: PRODUCT_IDENTITY_VERIFIED
• verify_point_support_surplus.py: PASS

V7 Staging Compliance

• All new types are pub(crate) with #[expect(dead_code)]
• Zero .unwrap()/.expect() in production paths
• Zero unsafe blocks
• No new public exports from packages/colors/index.js or index.d.ts
• Infrastructure only — no authority minting

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📥 Commits

Reviewing files that changed from the base of the PR and between da6f2d6 and e5f5d28.

📒 Files selected for processing (10)

• crates/labcolors-core/contracts/clean-set-srgb8-v1/receipt-v1.json
• crates/labcolors-core/contracts/clean-set-srgb8-v1/receipt-v1.sha256
• crates/labcolors-core/contracts/point-support-reference-surplus-q55-bps-proof-v1.json
• crates/labcolors-core/src/arena_lifecycle.rs
• crates/labcolors-core/src/field_arena.rs
• crates/labcolors-core/src/lib.rs
• crates/labcolors-core/src/observation.rs
• crates/labcolors-core/src/report_arena.rs
• scripts/_canonical_receipt.py
• scripts/verify_point_support_surplus.py

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