feat(console): add go usage endpoint - #16513

Upstream v1.18.16 (a3647eb) -> v1.18.17 (02546df), 32 commits.

Functional changes:
- fix(compaction): clearer instructions for smaller models like dsv4 flash (anomalyco#42045)
- fix(provider): add Merge Gateway reasoning variants (anomalyco#41867)
- fix(opencode): cap session retries with jitter (anomalyco#41939) - retry policy
  gains RETRY_MAX_RETRIES=5 global cap and 25% jitter
- fix(opencode): detect Copilot PDF input support (anomalyco#41522)
- fix(provider): scope DeepSeek V4 Flash sampling defaults (anomalyco#41620)
- fix(session): route all Muse family models to the Meta system prompt (anomalyco#41581)
- fix(app): use current default model (anomalyco#38603)
- feat(console): add go usage endpoint (anomalyco#16513) and r2 data catalog stats
- fix(ui): correct OC-2 weak icon color (anomalyco#41504)
- fix(i18n): use widely recognized developer terminology (anomalyco#41532)

Conflicts resolved: 30 package.json version bumps (rebranded 1.18.17-sscity),
bun.lock (took upstream, rebranded workspace entries via bun install), and
session/retry.ts (kept fork per-reason maxAttempts cap alongside upstream
RETRY_MAX_RETRIES global cap and jitter).

Co-authored-by: vimtor <[email protected]>

Co-authored-by: vimtor <[email protected]>

Co-authored-by: vimtor <[email protected]>

Co-authored-by: vimtor <[email protected]>

GET /zen/go/v1/usage merged in anomalyco/opencode#16513 and now answers
in production, so the parser no longer has to guess. The route returns
`{ usage: { rolling, weekly, monthly } }`, each window holding a status,
a floored percent and an ISO reset, and nothing else; the aliases and
dollar fallbacks written against the proposal are gone. A window marked
`rate-limited` reads as spent, since its floored percent can say 99.

A valid key on a workspace without Go answers 403 with an
EntitlementError, which now reads as no subscription instead of a
rejected key, and a 404 is drift rather than an outage. The cookie
still ranks above the key because only the console publishes dollars.

Co-authored-by: vimtor <[email protected]>

opencode exposes no plan limits, but opencode.ai has an undocumented
usage route (GET /zen/go/v1/usage, anomalyco/opencode#16513) that
answers the 5-hour, week and month windows with a status, a percent
and a reset time. The Agents panel, the status bar and its hover now
show them like Claude's and Codex's, a rate-limited window in red, on
the same refresh interval.

The key comes only from `opencode auth export` run in the temporary
folder: the active opencode-go API key, every other entry ignored. It
lives for that one request, goes to opencode.ai over https in the
Authorization header and nowhere else: never written, logged, shown or
passed to a child; zinc.json asks for net:opencode.ai only. A Settings
toggle, on by default, turns it off. Off, no key, a revoked or expired
key, a 403 or an answer the app does not know show « unknown », the
reason and the console link.

agents_go.sh drives a fake export and made-up route answers (nothing
goes to the network) and checks the fake key appears in no file of the
run: data, settings, output, scenes, child arguments and environment.
One read-only check against the real route returned three windows ok.

New-task: owner ZN-770 OpenCode Go usage read with the Go key