feat(timeline): add automation lane commands with unified reduction

[shipyard-local]

Summary

Adds InsertAutomationLane / RemoveAutomationLane transaction commands and unifies the transaction reduction helpers. Second slice of the Creative Timeline Engine Phase 2 attachment replay, stacked on PR-2 (#6428).

• Both commands validate their targets (sequence, track, and — for insert — the referenced device placement) before staging, allocate the lane and its points as owned Project identities, and emit inverse commands so undo, redo, and journal replay restore the lane, its points, and their tombstone ownership exactly.
• Automation lane payloads compare bit-exactly (float bits via std::bit_cast) — a re-authored point differing only in the sign of a zero is not treated as equal.
• The transaction reduction helpers (target_error, identity insert/deactivate planning, error construction) move into transaction_reduction_support so clip and automation reductions share one implementation; automation command reduction lives in transaction_automation_internal.

Re-based onto arch-prep's identity model (replay by intent)

Same as PR-2, this is a replay-by-intent, not a raw cherry-pick. The checkpoint threaded the dropped automation_lane_id field and used designated initializers on ItemLocation (now a non-aggregate). Re-based to the canonical parent_id:

• Identity ownership rides parent_id — a lane's parent is its track, a point's parent is its lane — built via immediate_parent_id (the single parent-computation path).
• target_error validates a located identity against an expected one whose parent_id is computed the one canonical way (strict on parent_id + coordinates, matching arch-prep's prior inline check); tombstone reactivation reuses ItemLocation::has_same_owner.
• All checkpoint designated-inits → positional constructors; DeviceParameterTarget::device_placement_id() accessor → the field (PR-2's rename).

Squash + build wiring

• a4503b18d (commands) squashed with 1d9c1f8c8 (reduction refactor): the refactor deletes the 21 lines a4503b18d added to transaction_internal.hpp, so that file nets back to its main content (verified identical) rather than churning through review.
• Wired both new sources (transaction_automation_internal.cpp, transaction_reduction_support.cpp) into all four source lists (lib, no-exceptions object lib, WAM, WCLAP) and registered test_timeline_automation_commands.cpp. In the original checkpoint split, transaction_automation_internal.cpp's wiring landed in a later commit; wiring it here keeps PR-3 self-contained and building.

Tests

• New test_timeline_automation_commands.cpp (6 cases): command compare/retain, float-bits collision, atomic insert publishing owned identities, insert undo/redo/replay preserving tombstone ownership, remove undo/redo/replay.
• Full Release build (all targets) green. Timeline + playback suites pass: pulp-test-timeline-commands 10224 assertions / 15 cases, pulp-test-timeline-transactions 4041 / 8, pulp-test-timeline-model 10395 / 25.

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https://claude.ai/code/session_01TVQHcnbg3t6TvXsdv6gXhS

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Machine	m3
Tab	Timeline v3
Directory	/Volumes/Workshop/Code/pulp-pr1
Session	c66f4a64-25ea-42e5-b184-d48611a066a2

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_{stamped 2026-07-21 12:24 UTC}