Add Quick print-to-PDF and exact document exports

[mberrys]

Closes #123.

Quick operators can now use File → Print to PDF and Export document. Print-to-PDF and current-page PNG/TIFF output use Core's transparency renderer, with explicit fidelity acknowledgment and renderer, resolution, color, revision, and artifact identity in the result. PDF export preserves the accepted correction's exact published bytes and links them to Core's existing mutation receipt; original-input exports verify the loaded source digest. Stale, cancelled, incomplete-render, permission-restricted, and source-overwrite requests fail before destination publication.

Scope follows the approved print-to-PDF and export choice. Native printer spooling is deferred. Annotation appearances remain an acknowledged fidelity limitation; raster output is a color-managed RGB composite. No Widgets or PrintSupport dependency, protected Core interface, or receipt schema changes.

Validation at head b9dccb3aa620820b6739542be2066f3d065314dd:

• Windows 11, Qt 6.11.1/MSVC 2022 Release: all 23 mapped CTest suites passed in the final check-change run (148.88 seconds), including the complete Editor host, Action List, product operator, shell keyboard, and workspace suites.
• Focused output tests: 10 passed, 0 failed, 0 skipped; exact original/corrected PDF bytes and receipt identity, visual PDF/PNG/TIFF output, stale/cancel fences, overprint acknowledgment, and fatal-render refusal.
• Final ProductQuickAccessibilitySmoke --preview-fixtures loop-preflight/testdata/fixtures passed with the edited QML, software rendering, and native_accessibility_backend_active=0.
• Command catalog, Quick policy, mirror parity, architecture, and adapter checks passed. Final-head python scripts/agent/check-change.py --base origin/dev --build-dir C:/Users/micha/AppData/Local/Temp/loop-issue123-build --report C:/Users/micha/AppData/Local/Temp/loop-issue123-proof.json passed: format, affected builds, clang-tidy, source/architecture contracts, and all 23 mapped suites. Static analysis passed the configured policy; it still emitted existing/header diagnostics.

The focused visual fixture command was UnitTestsEditorHost.exe outputBytesAndFences outputPublishedPacket outputRenderFormats outputOverprintWarning outputRenderFailure fixJourneyPublishesOnlyAnApprovedPlanBoundToTheDisplayedIdentity with the Qt runtime on PATH and QT_QPA_PLATFORM=offscreen. The external native-test log records these per-run identities:

Output	Fixture PDF SHA-256	Output SHA-256
Print PDF	370bc05952f29a458ba6904fb48f7c4dbee41261c4026deaa390e89c81c6e7c4	9a7aef9c3d822a62edd0207cea72da86d118cc8f07ed6d578e6b6d2e213f0129
PNG	370bc05952f29a458ba6904fb48f7c4dbee41261c4026deaa390e89c81c6e7c4	6a32647618b13a2dcc0a1791bde9893b58c0a14fa26ec245af0e0dfe079cd70e
TIFF	efe6c17a79011eb3988527112d73efb555d37e79f13b7192f6b8fa9193dce3ac	8c3b7e0f8e9be72fbf24b589904fe059c8765700a4a35471bb0bdf64e806d7a5

The tests reopen and render the print PDF, check black/white content and page geometry, verify raster pixels/resolution, and compare output hashes. PDF fixture and print hashes vary with generated PDF metadata.

Hosted checks at the same head: CodeQL, Documentation truth, and Supply Chain Policy passed. CI run 38089727912 remains in progress.

Draft qualification boundary: clean-machine Windows and Linux print-to-file lanes have not been performed. The local Quick smoke used software rendering and reported native_accessibility_backend_active=0. This PR does not claim those lanes or print proof.

Anti-slop review: reused Core rendering, artifact identity, governed publication receipts, and the safe writer. Removed stale explanatory test comments and added an explicit render-error refusal; retained cancellation, revision, provenance, and atomic-publication checks.