feat(gui): add draggable split panes to Remote Workspace

[flam-ing]

Summary

• Add a session list and up to four draggable conversation panes to Remote Workspace in the browser dashboard and Tauri shell. Sessions retain independent drafts, requests, errors and Stop state; closing a pane changes only the view.
• Restore the per-Hub split tree and divider sizes. Dividers support the appropriate arrow keys plus Home/End, and pointer resizing focuses the divider. At viewport widths up to 760px, panes stack without resize dividers or nested horizontal scrolling; widening restores the saved layout and sizes.
• Keep @flam-ing's original implementation (0c0101295b608be3275a72e5e9e97c639f640408), merge origin/dev at 7640a942b35044c974e534b84d5a8049f4a8ae9a, and add the narrow-screen/focus fixes and persistence regression coverage. Review commit cf49793c4 fixes nested side-by-side splits: every row split had a fixed 528px minimum, so splitting right three times hid two panes behind a horizontal scrollbar inside a pane column at the 1100px desktop default (and at any width up to ~2000px). A track holding a nested split now reserves that subtree's minimum width; leaf panes still follow the saved ratio, and an oversized tree scrolls the pane surface once. Update the English/Korean guides and ownership documentation. No new repository dependencies.

Verification

Current head cf49793c41b9cb3457ab88a0271b0d61ab89e58d (0 behind dev 7640a942b).

• Review round (head cf49793c4): cd gui && bun run test 3,339 passed, 0 failed, 344 files; focused split/workspace files 23 passed, 0 failed; gui tsc --noEmit -p tsconfig.app.json, bun run lint, bun run lint:i18n, root bun run build:gui, bun run typecheck, bun run structure:check, bun run privacy:scan, git diff --check passed. Browser (Chrome Headless Shell 154 against the built GUI on a sandboxed proxy, port 18791, synthetic /api/remote-workspace responses): real mouse drag moves the divider 50→70 with the separator focused, clamps at 80 past the container edge, stops on release; ArrowLeft → 75, persisted and restored after reload; 700px stacks with no divider and 0px document overflow, widening restores 75. Four panes split in one row at 900/1100/1280px: before the fix 2 split children overflowed sideways; after, 0 overflow, all panes 260px, one surface scroll (1,064px). A two-pane 0.75 split renders at 74%. Root test:changed was not rerun for this GUI/CSS-only commit.

The items below are the earlier validation of head 2b49b5eabb0df0497828a96230f4700b9650642c. Every local test and proxy used fresh OPENCODEX_HOME=$(mktemp -d) and CODEX_HOME=$(mktemp -d); screenshot proxies listened on ports 18677 and 18678. Bun test runner: 1.4.3.

• Focused GUI: cd gui && bun ../scripts/test-with-pinned-bun.ts --isolate tests/remote-workspace-split.test.tsx tests/remote-workspace-split-layout.test.ts tests/remote-workspace.test.tsx: 22 passed, 0 failed, 3 files. Covers both resize axes, Home/End bounds, restored sizes, draft exclusion, cold-load restoration, session-scoped requests and late Stop responses.
• Full GUI: cd gui && bun run test: final unchanged-head rerun 3,338 passed, 0 failed, 344 files. The first full run had 3,337 passed, 1 failed in the unchanged remote-link.test.tsx test “discovery loading, empty setup and rescan retain keyboard-accessible manual entry” (focus at line 927). bun ../scripts/test-with-pinned-bun.ts --isolate tests/remote-link.test.tsx then passed 48/48 on both this head and clean origin/dev. The clean-dev full GUI suite passed 3,328/3,328, and the final PR full rerun passed as above. No unrelated focus code was changed; this records the transient full-run failure rather than treating the initial run as green.
• Import-connected root tests: OCX_TEST_NO_QUEUE=1 bun run test:changed: 212 passed, 0 failed, 14 files, against the origin/dev merge base above. The first queued attempt was cancelled while another worktree held the user lock; the explicit short overlap completed successfully.
• Root gates: bun run typecheck, bun run structure:check, bun run privacy:scan, and git diff --check passed. bun test tests/ci-workflows/file-size-ratchet.test.ts: 9 passed, 0 failed. The initial structure check caught a 602/600-line desktop document after the dev merge; clean dev passed, and condensing this PR's note restored the budget.
• GUI: cd gui && bun run lint, bun run lint:i18n, and root bun run build:gui passed. Vite retains its large-chunk warning. The clean origin/dev GUI build also passed for the before capture.
• Docs: cd docs-site && bun install --frozen-lockfile && bun run build passed: 577 pages, 81,206 internal links checked.
• Browser: Production GUI builds served by the sandboxed proxies, using synthetic session API snapshots. Native mouse drag splits a listed session and moves a visible pane without duplication. Keyboard resizing on both axes, Home/End, pointer resize/focus, four-pane restoration after reload, exclusion of unsent drafts, 390px/760px stacking and desktop restoration passed with no browser page errors. No live model turn or remote Executor was exercised.
• Browser limitation: Playwright could not launch /Applications/Google Chrome.app (browserType.launch: Timeout 10000ms exceeded.). Captures and browser checks therefore used GOAT's installed Chrome Headless Shell 154.0.8037.92, driven by playwright-core installed only in scratch space outside the repository.
• Native limitation: rustfmt is unavailable locally; its check and native desktop compilation/OS-webview drag/drop were not validated here. The native change disables Tauri's native drag/drop interception so HTML pane dragging reaches the dashboard. Native platform evidence remains for CI/maintainer acceptance.
• Full root-suite exception: Other worktrees are testing concurrently. The full runtime suite was not run; the focused GUI coverage, full GUI attempts, import-connected root tests and explicit source/document gates cover this local scope. Broader runtime/native coverage remains for CI.
• Exact-head cross-platform CI: Cross-platform CI — workflow_dispatch on ci/pr-6767 on cf49793c4 (the earlier 2b49b5eab run was cancelled as superseded). Dispatched with gh workflow run ci.yml --repo lidge-jun/opencodex --ref ci/pr-6767; queued at handoff, not passing evidence. The PR remains draft; no merge is authorized by this validation.

Before — real origin/dev build at 7640a942b35044c974e534b84d5a8049f4a8ae9a, synthetic session snapshot:

After — real PR-head build at 2b49b5eabb0df0497828a96230f4700b9650642c, the same synthetic sessions:

After — 390px viewport with stacked panes:

After the nested-split fix — head cf49793c4, 1100px desktop default, four sessions split right in one row, pane surface scrolled to its end (every pane reachable through one surface scroll):

Screenshots are committed only on pr-assets, never on this PR branch.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

Review readiness checklist

This contributor PR remains draft pending CI and maintainer/native acceptance.

• Required local validation passed; commands, results, and any full-suite exception are documented.
• I pushed my PR to a recent dev commit (at most 10 behind; a maintainer may still ask for the exact tip before merge).
• I resolved all correct Codex and CodeRabbit findings.
• My PR is ready for review.

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Review readiness checklist

• ⬜ Required local validation passed; commands, results, and any full-suite exception are documented.
• ⬜ I pushed my PR to a recent dev commit (at most 10 behind; a maintainer may still ask for the exact tip before merge).
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[lidge-jun]

Being carried into #7223 with your authorship preserved; this PR will be closed when the bundle lands.

[lidge-jun]

Landed on dev in a8d1bb8 via #7223 (your change is its own commit in that bundle, and the squash keeps your authorship as Co-authored-by). Thank you!