docs(docs-next): port api reference (phase 3)

[pratyush618]

Phase 3 of the docs migration — port the full API reference (14 pages, ~2300 lines) from the Zensical site into the new Fumadocs site at `docs-next/`. Zensical site at `docs/` still ships unchanged.

What's ported (14 pages)

Top-level API reference (1 page)

• `docs/api/index.md` → `docs-next/content/docs/api-reference/overview.mdx`

Queue subsection (6 pages, lives at `/docs/api-reference/queue/...`)

• `docs/api/queue/index.md` → `queue/index.mdx` (constructor, task registration, enqueue methods)
• `docs/api/queue/jobs.md` → `queue/jobs.mdx` (get, list, cancel, archive, replay)
• `docs/api/queue/queues.md` → `queue/queues.mdx` (rate limits, concurrency, pause/resume, stats, dead letters)
• `docs/api/queue/workers.md` → `queue/workers.mdx` (run_worker, hooks, circuit breakers, async map)
• `docs/api/queue/resources.md` → `queue/resources.mdx` (worker_resource decorator, register_type, locking)
• `docs/api/queue/events.md` → `queue/events.mdx` (on_event, add_webhook, task_logs)

Standalone API classes (7 pages)

• `docs/api/task.md` → `task.mdx` (TaskWrapper)
• `docs/api/result.md` → `result.mdx` (JobResult)
• `docs/api/context.md` → `context.mdx` (current_job, JobContext)
• `docs/api/canvas.md` → `canvas.mdx` (Signature, chain, group, chord, chunks, starmap; 3 mermaid diagrams)
• `docs/api/workflows.md` → `workflows.mdx` (Workflow builder, WorkflowRun, gates, sub-workflows, types)
• `docs/api/testing.md` → `testing.mdx` (TestMode, TestResult, MockResource)
• `docs/api/cli.md` → `cli.mdx` (worker, info, scaler commands)

Conversion rules applied

Source	Destination
`# Title` (h1)	YAML frontmatter `title:` + `description:`
`::: taskito.foo.Bar` (mkdocstrings autodoc)	dropped (no Fumadocs equivalent yet — phase 7 may revisit)
`!!! tip "Sub-pages"` / `!!! warning`	`` / ``
`(other-page.md)` / `(../guide/...)`	`/docs/api-reference/...` / `/docs/guides/...` (re-IA'd)
`int | None` in markdown tables	`int | None` (escaped pipe so MDX doesn't break the table)
```mermaid``` fences	`` (existing component from phase 2)

Design decision: TypeTable deferred

The original plan called for a custom `` component to make every page a single declarative invocation. After surveying the source, I decided to keep markdown tables for now — they render cleanly in MDX, and Fumadocs already ships `` for cases where we want richer type-level UI.

Adopting `` (or a custom ``) wholesale would have made this PR ~3x larger and risked introducing inconsistency mid-port. A follow-up PR can incrementally upgrade the high-traffic constructor + method tables to `` if/when we want the polish, without blocking phase 4.

Test plan

• `pnpm types:check` — clean
• `pnpm lint` — exit 0 (2 known scaffold-CSS warnings, no errors)
• `pnpm build` — 89 static pages now (up from 75 in phase 2), no warnings, no errors
• `out/llms.txt` and `out/llms-full.txt` regenerated with the new API surface
• CI: `Build Docs (Next)` job stays green
• Manual smoke once merged: spin up dev server, click through all 14 API pages, verify Mermaid diagrams render in canvas.mdx, verify Callouts render correctly

Commits

1. `docs(docs-next): port api-reference overview + queue subsection` — 8 files (overview + queue/* x 6 + meta)
2. `docs(docs-next): port api-reference standalone classes` — 7 files (task, result, context, canvas, workflows, testing, cli)

What's NOT in here (next phases)

• Long-tail port: guides (9 sub-categories), examples, comparison, faq, changelog (phase 4)
• Landing page polish + shadcn-style components (phase 5)
• LLM-friendly routes ← already in template
• Cutover / decommission Zensical (phase 7)