feat: draw, reshape, remove and relabel grid lines (T01.2) - #417

T01.2: drawn grid lines and relabelling

Verdict: approved. No changes requested.

Reviewed the delta over #416 (13 files, +1264): the typed GridLineEditRequest model with versioned fingerprints, the pure engine edit decisions, the Change::Grid authoring/validation path, the four CLI commands, the initial drawn line at creation, and the E2E suite.

What checked out:

• Atomicity and guards. Each operation validates the complete replacement record; frame, grid name and family modes are verified unchanged by the change validator (mode conversion refused with GRID_FAMILY_MODE), identities and geometry survive relabel, the last line cannot be removed, and a line named by an incoming reference is DEPENDENCY_CONFLICT. The engine never mutates its input; the footprint (reads of target lifecycle/shape/placement plus the fresh axis absence, one shape-input write) matches the validator declared groups, and check_footprint ties them together.
• Geometry. World points convert through the pinned frame with the exact inverse rotation, then re-validate against the local 1e6 cap and 1 mm floor; degenerate and colliding identities refuse without writes. The rotated-frame E2E pins the conversion.
• Replay. Fingerprints are independent of source state, so an exact retry replays from operation evidence without resurrecting a later-removed line — covered end to end, including undo/redo units.
• Creation reachability. create-grid --u-from/--u-to/--u-label makes a drawn family with one line reachable at creation without storing an invalid empty grid — this also unblocks the GR-P14 shape of test case against the amended contract proposed in #415; the contract text (section 8.1 drawn-empty) should pick that up there.
• Documentation. The design note states the conservative reference blocking (grid-level until axis-specific stored references arrive with W01), the replay rule and the unclaimed parent gate.

Minor observations, no change needed: a non-grid target reports UnsupportedProperty where NotFound might read better; the conservative removal guard refuses any line removal while the grid itself is referenced (safe over-refusal, already documented as a W01 follow-up); the relabel-family CLI counts labels only to satisfy the parser, the real count check lives in the engine where it belongs.

Tests, fmt and clippy were not run in this review; CI covers them.