feat(opencode): add OpenCode Go quota tracking provider

[hiyukoim]

Summary

Replaces closed #102 since it got messy. Rebuilds OpenCode Go as a quota provider on current upstream/main (keeps Kimi / Moonshot / DeepSeek), following the existing provider pattern from CONTRIBUTING.md. Related: #100.

• Agent + tracker + SQLite store for OpenCode Go snapshots (5-hour / weekly / monthly)
• Dashboard tab, charts, deep insights, menubar card, settings UI
• Config via OPENCODE_GO_WORKSPACE_ID + OPENCODE_GO_AUTH_COOKIE (see docs/OPENCODE_SETUP.md)
• OPENCODE_ENABLED remains the separate Codex-via-OpenCode-auth path
• Frontend contract: quota JSON uses limit (not limitValue); empty-state re-render guarded; dedicated history routing

Why a new PR

#102 was closed after an unrelated-histories merge onto the harden branch corrupted history / app.js. This branch starts clean from upstream/main and ports OpenCode-only changes.

Provider checklist

Per CONTRIBUTING "Adding a New Provider":

1. internal/api/opencode*.go
2. internal/store/opencode_store.go (+ schema in store.go)
3. internal/tracker/opencode_tracker.go
4. internal/agent/opencode_agent.go
5. Endpoints in internal/web/handlers.go / opencode_handlers.go
6. Dashboard tab + charts in internal/web/static/app.js

Test plan

• Focused short tests: api, web, agent, store, tracker, config
• go vet ./...
• CI green on this PR
• With OPENCODE_GO_WORKSPACE_ID + OPENCODE_GO_AUTH_COOKIE set: OpenCode tab appears, quotas poll, charts update
• Without OpenCode env: other providers unchanged, no OpenCode tab noise

./app.sh --smoke
# optional full suite:
./app.sh --test

[codecov]

Codecov Report

❌ Patch coverage is 41.98473% with 760 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/web/opencode_handlers.go	20.54%	307 Missing and 14 partials ⚠️
internal/store/opencode_store.go	37.78%	193 Missing and 26 partials ⚠️
internal/tracker/opencode_tracker.go	54.19%	51 Missing and 20 partials ⚠️
internal/api/opencode_client.go	77.06%	38 Missing and 12 partials ⚠️
internal/web/handlers.go	11.90%	34 Missing and 3 partials ⚠️
internal/agent/opencode_agent.go	51.51%	27 Missing and 5 partials ⚠️
main.go	14.28%	11 Missing and 7 partials ⚠️
internal/config/config.go	45.45%	4 Missing and 2 partials ⚠️
internal/web/menubar.go	0.00%	5 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[prakersh]

Thanks for the clean rebuild - this follows the provider pattern well and the limit-key regression test from #102 is appreciated. CI is green. A few things before merge:

1. Auth vs parse errors: the client follows redirects, so an expired cookie likely hits a 302→login page→200 and surfaces as ErrOpenCodeParseFailed instead of ErrOpenCodeUnauthorized. Setting CheckRedirect to http.ErrUseLastResponse and mapping 3xx to unauthorized would fix this (also keeps the cookie out of redirect chains).
2. False cycle resets in fallback mode: the data-slot parser has hour granularity, so recomputed ResetsAt can jump ~59 min between polls - past the 10-min threshold in the tracker, spuriously closing weekly/monthly cycles. Suggest a wider threshold (~90 min) or requiring a utilization drop.
3. TestOpenCodeAgent_Poll_FetchErrorNoInsert hits the real opencode.ai - please use the stub client or an httptest server; tests here must be hermetic.
4. Cookie heuristic: Contains(cookie, "=") misfires if the raw value contains = (base64 padding). Prefer an auth= prefix check.
5. Late-appearing quotas never render: cards render once, then update by ID - if monthly shows up after the first render, it gets no card until reload. Re-render when the incoming quota set differs from the rendered cards.