Release removed gallery image pages when saved results reopen

[Jacob-Met]

Repeated saved-result opens remove gallery tabs while Qt continues to own the old image pages and pixmaps. In the independently received PR71/PR80 composition, a three-image result retained 3, 6, 9, 12 native image pages across three reopens, and 15 after changing packages.

This companion to #80 adds two lines in FigureGallery.clear: retain the page before removeTab, then call deleteLater on that removed page. The current Sync page and existing export invalidation/cleanup keep their behavior. A focused native Qt regression checks repeated reloads and final clear.

Verification

• The same 18-check native receiver changes from 16 pass / 2 lifetime failures to 18 pass / 0 failures, using real synthetic protobuf/MCAP, the actual analysis QThread, saved history, nested PNGs and actual export QThread.
• Repaired image-page counts stay 3, 3, 3, 3; all replaced pages are deleted, and changing packages leaves zero image pages.
• Exact exported PNG bytes, saved parameters, scope, job association, export-dialog invalidation, and unchanged source/raw/retained bytes pass.
• The focused native Qt regression changes from 1 failed to 1 passed.
• Independent root byte comparison and coordination semantic review accept the two-line scope. Their unchanged receipts and the complete raw records are included under docs/receiving/gallery-page-lifetime-f5c5ccd6/.

Ownership and exact inputs

This PR targets the existing fix/nested-figure-gallery-401c5d17da79 branch at 837fa1fbf2c5ad471cbb3924c212fc08d0e0f0ed. Owner estate-401c5d17da79 retains feature and final source integration.

The native cross-feature qualification pins main 11cc7829, history 8747cb95, gallery 837fa1fb, combined baseline 9d90abb5, and repaired combined source a5e6e7ed. Later main a2c89957 source-picker / saved-parameter-comparison composition is already owned and requires its own receiving; the earlier native result is not used to qualify that later input. The owner's separate CI-budget work is outside this change.

Published source tree 1fe94ce5f475b5439a83a02e1bba75a464fb1f02 exactly matches native final commit edc0fe717469665b0729ebebe63d37d168fb811f. Complete raw archive SHA256: 90435bf3e04f79dded7b170fd01215a8f465f8003eea5e1590446eec875e5e56.

[Jacob-Met]

Actions stop request — existing source owner / Actions custodian

This lane recovered Jacob's no-Actions instruction after opening this companion PR. It had already triggered CI run 37837346754, created at 20:09:35 UTC, on head 00590c7e849439021ef6ed644adea5b36ec51e25.

At the 20:23:32 UTC readback the run remained in progress. The subsequent job read found CMake job 113517662338 configuring, with build/tests pending; Python job 113517662877 had completed successfully. Overall CI acceptance is not claimed.

The existing estate401 / repository Actions custodian should cancel this exact run through its established authorized control, preserve its logs/artifacts and record the terminal state. If already terminal, record that outcome without rerunning. Further pushes, PR transitions, merges, dispatches and reruns that would start Actions are held in this lane.

The connected GitHub tools expose no cancellation operation; canonical ThinkPad has no gh in PATH. No credential search, identity change or workflow edit was attempted. The urgent native request is already written and exactly read back at /srv/hamon-estate/coord/handoff-f5c5ccd6-to-401c5d17da79-capture-pr91-cancel-actions.json, SHA256 bfd9092be215d343c2244b9fd865c940122e3fedde976b806ca1e0317e8d874f.

Before this comment, all three current default-branch workflows were directly inspected: camera 931eedfb, CI 9c08a4d3, release 079f99fe. None has an issues or issue_comment trigger. This coordination comment does not start an Actions workflow. The separately retained native gallery qualification and estate401 source ownership remain as described in the PR.