feat: statusline provider usage + session workspace actions SDK

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Summary

Adds the core/gateway/desktop plumbing needed by the external Desktop plugin hermes-statusline-workspaces:

• JSON-safe, credential-free serialization for provider account usage snapshots
• JSON-safe live rate-limit state serialization + OpenAI-compatible reset duration parsing
• Persistent session.workspace.set RPC (durable session id, optional profile, busy-session guard)
• Desktop SDK contribution area session.actions plus curated host helpers:
  • host.selectWorkspaceDirectory
  • host.setSessionWorkspace
• SDK docs updated accordingly

Companion plugin

• Repo: https://github.com/Codezilla-jpg/hermes-statusline-workspaces
• Release: https://github.com/Codezilla-jpg/hermes-statusline-workspaces/releases/tag/v0.1.0

Notes / follow-ups

• Gateway RPC usage.providers is still a planned follow-up for a single combined account+rate-limit payload.
• Rate-limit overflow/edge-case hardening can still be tightened further.

Test plan

• tests/agent/test_account_usage.py (serializer + account suites)
• tests/agent/test_rate_limit_tracker.py
• tests/tui_gateway/test_session_workspace_set.py (+ adjacent session/cwd suites)
• Desktop: session-actions-menu.test.tsx, typecheck on touched surfaces
• CI full matrix

[teknium1]

Thanks for the focused SDK and session-workspace groundwork. Two integration gaps need resolution before the companion plugin can work end to end.

Problems

• apps/desktop/src/sdk/index.ts:128-131 routes to a profile gateway but does not send profile in the RPC params. The handler selects its database through _profile_db(params) (tui_gateway/server.py:1209-1218), so app-global remote mode can target the launch profile rather than the row's profile.
• agent/account_usage.py:57-81 and agent/rate_limit_tracker.py:106-122 add serializers, but no usage.providers handler is added. The linked plugin calls host.request('usage.providers', ...), so its provider status path remains unavailable.

Suggested changes

• Forward profile in the workspace RPC params and add a cross-profile durable-id test.
• Add and exercise the combined provider-usage RPC, or split that unfinished statusline integration from this PR.

This is an automated hermes-sweeper review.

[teknium1]

requestGatewayForProfile changes the socket, but this handler selects its database from params['profile'] (_profile_db). App-global remote mode can share one backend, so please include profile: change.profile in this payload and cover the same durable id existing in two profile DBs.

[teknium1]

This serializer is not exposed by a gateway RPC in this PR. The linked companion plugin requests usage.providers, so it cannot consume this output yet. Please add and test that endpoint here, or split the unfinished provider-statusline portion.

[alt-glitch]

This was generated by AI during triage.

Related: #58339 (provider account/rate-limit usage surface), #33094 (provider-usage request), and #66484 (Desktop plugin workspace capability). This PR combines a distinct Desktop-plugin session-actions SDK with profile-aware durable workspace mutation; the public API contract needs maintainer direction.

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Rückgängig gemacht - Plugin soll privat bleiben.