feat(browser): per-tab persistence + legacy state.json retirement

[BunsDev]

Summary

Layer C of the per-tab browser work (builds on Layer A 9de9e07 visibility fix and Layer B e59094e4 per-tab data dir, both already on main).

• SQLite-backed browser pane persistence. New browser_panes table keyed by stable per-pane UUID; LeafContents::Browser(BrowserPaneSnapshot { session_id, state }) is wired through app-state save/restore and launch-config conversion. Browser panes now restore into the same workspace tab they were opened in, with the same intra-pane tab list and WebKit data-dir identity.
• Retire the legacy ~/.warp/config/browser/state.json JSON path. The old single-pane-into-tab-0 fallback is redundant with SQLite app-state restore and could create duplicate panes if both paths fired; this removes the legacy module, restore/write callsites, and close-time JSON writes.
• One-shot launch cleanup plus UUID hardening. Startup deletes any orphaned legacy browser/state.json, and restored browser session IDs are validated as UUID v4 values before they can be used as data-dir path components.

Test plan

• cargo fmt --check
• ./script/check_ai_attribution
• ./script/check_rebrand
• git diff --check origin/main...HEAD
• cargo test -p warp-app browser::data_dir --features gui
• cargo check -p warp-app --bin cast-codes --features gui
• Manual: open browser pane in tab 1, navigate to a site, fully quit the app, relaunch; pane returns in tab 1 with the same tab list and active tab.
• Manual: open browser panes in two workspace tabs and confirm Linux/Windows data-dir isolation. On macOS, wry 0.38 still uses WKWebsiteDataStore.defaultDataStore, but the per-pane directory is created for future plumbing.
• Manual: with legacy ~/.warp/config/browser/state.json present, launch once and confirm it is removed; relaunch and confirm the cleanup is idempotent.

[Copilot]

Pull request overview

Adds SQLite-backed persistence for embedded browser panes, replacing the legacy single JSON browser/state.json restore path with per-pane snapshots tied to app-state restoration.

Changes:

• Adds browser_panes schema/model/migration support and wires browser panes through app-state save/restore.
• Updates browser pane/view snapshots to carry stable per-pane session IDs and browser tab state.
• Removes legacy JSON persistence and adds best-effort cleanup for old browser/state.json.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/persistence/src/schema.rs	Adds Diesel schema for browser_panes.
crates/persistence/src/model.rs	Adds browser pane persistence model and constants.
crates/persistence/migrations/2026-05-26-160000_add_browser_pane/up.sql	Creates browser pane persistence table.
crates/persistence/migrations/2026-05-26-160000_add_browser_pane/down.sql	Drops browser pane persistence table.
app/src/workspace/view.rs	Removes legacy browser restore/write path and creates new pane UUID sessions.
app/src/persistence/sqlite.rs	Saves/restores browser panes through app-state SQLite.
app/src/pane_group/pane/browser_pane.rs	Snapshots browser panes into app-state.
app/src/pane_group/mod.rs	Restores browser panes from app-state snapshots.
app/src/launch_configs/launch_config.rs	Excludes browser panes from launch-config conversion.
app/src/browser/persistence.rs	Removes legacy JSON persistence implementation.
app/src/browser/mod.rs	Removes legacy persistence module export.
app/src/browser/data_dir.rs	Adds cleanup for the legacy state file.
app/src/browser/browser_view.rs	Stores session IDs in browser views and removes legacy close persistence.
app/src/app_state.rs	Adds browser pane snapshot type and marks it persisted.

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