Audit foundational specs and fix Tool recovery and Workspace drop ownership

[nedtwigg]

Saved sessions with multiple Tools and rejected geometry currently generate an invalid fallback layout, so engine hydration turns Tools into plain terminals. Normalize that layout and test the complete restore-to-engine path. Also gate file-drop callbacks to the active Workspace so hidden mounted Walls cannot receive input.

Audit glossary, Lath, layout and shortcut contracts against their implementations and tests. Correct helper/primary Surface cardinality, hidden Workspace lifecycle, kill ordering, restore compatibility, navigation edges, entry direction, save coalescing, clipboard dispatch and modifier timing. Move local shape/mechanism inventories to canonical types and comments while preserving cross-module invariants and Future designs; ratchet the reduced word budgets.

Make the prose audit include companion contracts, rationales and rationale-only source references. Fix Windows import resolution in the public-doc lint so its checks reach transitive components.

Validation:

• 213 focused library tests across 9 files and library typecheck passed.
• Both new behavior regressions failed before their fixes and passed afterward.
• 7 isolated audit/import-graph tests passed; public-doc lint passed all 15 checks.
• Spec lint, spec mutation self-tests, xterm, loopback, deploy, PowerShell and remote structural lints/self-tests passed in an isolated checkout.
• Visible innerdogfood inspection confirmed hidden Workspace Wall retention and terminal DOM detachment. Native Tauri drag/drop is disabled in the shipping configuration; its callback ownership is covered by the regression test.

Stack: first chunk, based on fresh origin/main ac7a2d3. The remaining domain audits and fixes continue in dependent PRs.

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