fix(frontend): keep the open workspace/channel across a reload

[haowei2000]

Change description

Refreshing the page dropped you back into the personal workspace, no matter which team workspace you were reading.

The chat route was /chat/* and carried no selection, while selectedWorkspaceId lived only in memory (chatStore persists just lastChannelByWorkspace). After a reload it was therefore always null, and ChatLayout's bootstrap fell back to the personal workspace unconditionally. The same gap meant a channel could never be linked or shared — the URL was always just /chat.

This puts the selection in the path (/chat/:workspaceId?/:channelId?) and makes that the source of truth across reloads.

The store stays the sole selection API, so all 11 call sites (rail, sidebar, dialogs, invite/register flows) are untouched. ChatLayout reconciles the two in one place: path → store on mount and back/forward, store → path for in-app selections. hydrateSelection applies an explicit pair without selectWorkspace's last-channel derivation, which would otherwise clobber the channel the path names.

Two things worth a reviewer's attention

The mirror navigates with replace, not push — a deliberate trade-off. On mobile the conversation screen is itself a pushed history entry (openChatScreen), so adding one per channel switch would make Back land on the previous channel instead of popping to the channel list, breaking the existing back gesture. Refresh-restore and shareable links both work; browser back/forward between channels is knowingly not wired up, since that needs the mobile history model reworked first. location.state is carried through the mirror for the same reason.

A latent race in loadWorkspaces — it read selectedWorkspaceId through its mount-time closure, which the path now races: the captured null would land when the request resolved and overwrite the workspace the URL had just restored. It now reads fresh via getState(), and also validates membership, so a stale or foreign link falls back home rather than resting on a workspace that renders empty.

Change type

• Bug fix (fix)

Test

• Unit tests added/updated
• Front-end npm run build no error reported
• Verified end-to-end against the kind stack (vite dev → in-cluster gateway, real login)

Manual verification:

Scenario	Result
Reload while on team workspace parity-ws	Stays on parity-ws (previously bounced to Personal)
Reload while #claude-smoke is open	Channel restored, cold-load deep link works
Non-member workspace id in the path	Falls back to personal workspace and corrects the URL

pytest is N/A — the Python backend is gone (gateway-only per docs/arch/ARCHITECTURE_OVERVIEW.md).

Note for anyone pulling this branch: the worktree's node_modules was stale and missing yaml, which white-screened vite and broke tsc. npm install fixes it; package-lock.json is unchanged. The two pre-existing PdfViewer.tsx pdf.js type errors are untouched and out of scope.

Database migration

• Does not involve database changes

Security and Release Impact

• Does not contain .env, logs, databases, uploaded files, private keys, tokens or production configurations
• Updated documentation when it comes to configuration, deployment, permissions, file uploads, or Agent Bridge — N/A, no config/deploy surface touched

Related Issues

Closes #

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