Let node reruns recover from earlier attempts

[SaladDay]

What

Node reruns and uninstall recover from earlier attempts (review-node F1-F10).

• F1: a rerun on a registered node writes the unit and proxy settings and restarts the service before the node step, so it applies even when that step stops (changed configuration, newer node program).
• F2: the root record is written with pending before the node step and rewritten without it after registration. A pending record behaves as no record: the rerun fetches with the token, repeats host checks and replaces the record. Records without pending (existing nodes) stay registered.
• F3: a differing unit is replaced and the service restarted.
• F4: the 401 hint points to Clean up a host on the Nodes page, no path.
• F5: the microsandbox store is deleted only when the node had registered state (so Core was asked); otherwise it is kept.
• F6: drop_runtime_archives also drops the partial files.
• F7: nodes.md (EN+zh) disk row says the download resumes.
• F8: the store link check now runs in confirm_removed, before the unit or files are touched, so "Nothing was changed" is true.
• F9: dialog comment matches the text; closing Clean up a host leaves focus to the dialog's restore; heading focus only after a removal.
• F10: removed the network branch of load_manifest, distribution.NoRedirect, install_display.busy and their tests.

No new flag, setting or command; pending is a record field set only while an attempt is unregistered.

Verification

• python3 -m unittest discover in deploy/node: 158 OK (1 skipped, pre-existing)
• pnpm --filter @oac/web typecheck: OK; vitest run sandbox-page-ownership.test.tsx: OK
• node --test website/tests/translations.test.mjs: tests 1-2 pass; test 3 needs vitepress, skipped
• python3 scripts/check-names.py: OK

New tests: proxy applied when the node step stops (F1), unregistered attempt pins nothing (F2), changed unit replaced (F3), store kept when Core was never asked (F5), linked store refused before removal (F8).

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