docs: reshape canonical first-session and troubleshooting journey

[CompleteDotTech]

Summary

Reshape the two docs-owned journey pages so coven-docs is the progressive end-user path issue #775 asks for:

• guide/getting-started now walks the whole first-session journey in order: install and verify (npm install -g @opencoven/cli → coven --version → coven doctor), connect a harness (coven setup codex|claude|copilot), run one recorded session (coven daemon start → coven run codex "explain this repo in 5 bullets" → coven sessions), inspect the record (coven sessions show/events/log, coven attach, coven status), then a new Recover when a step fails leg and an explicit Advanced next steps table (provider setup, harnesses, daemon, deployments, sessions, local API, memory as preview, hub/scheduler) plus coven help --all for the full grouped command surface. The old flat "Continue" list is replaced by that grouped expansion.
• reference/troubleshooting becomes the explicit recovery leg of the journey: a new Recovery rules section (fix the first failing branch, rerun doctor, inspect before you mutate, sacrifice permanence) and a journey-stage → section map (install → harness → daemon → run → session). The existing ordered decision tree, error-code lookup, and all failure sections are unchanged, so every existing anchor stays valid.

Docs-only diff (2 files, +80/−15). No CLI-reference pages touched.

Issue

Refs OpenCoven/coven#775 (child of OpenCoven/coven#670). Closes OpenCoven/coven#775 on upstream merge (cross-reference — GitHub cannot auto-close a coven issue from this repository).

How claims were verified

• Commands, flags, and subcommands checked against OpenCoven/coven@main (1364cec9dbaf1e2aca2e4544dec0e1ce807d859c): crates/coven-cli/src/main.rs (doctor, setup + Selector::{Codex,Claude,Copilot} and --verify, daemon start/status/restart/stop, run with --cwd, sessions {search,show,events,log} with --plain/--manage/--all, attach, archive, sacrifice --yes, summon, status, pc), crates/coven-cli/src/help.rs (coven help --all), crates/coven-cli/src/pc/mod.rs (status/top/disk + --confirm relief).
• Stability labels respected per docs/site-manifest.json: guide and reference are stable and owned by OpenCoven/coven-docs; memory-models is labeled "(preview)" in the advanced table; no experimental work is presented as supported.
• Required getting-started onboarding mentions from scripts/check-cli-docs.mjs are preserved verbatim.

Test plan

• pnpm run typecheck (after pnpm exec fumadocs-mdx to regenerate .source)
• pnpm run check:content (site-manifest, source-lock, english-only, no-leading-h1, product-scope, fumadocs, daemon/cli/coven-code/harness/memory docs contracts, mermaid parse — 14 diagrams valid)
• pnpm run check:links — 0 errors
• pnpm run check:anchors — passed across 86 MDX pages
• pnpm run check:automation, pnpm run check:generated, pnpm run test:api-runner (23 pass)
• git diff --check
• pnpm run build (Next.js production build) — deferred to CI
• pnpm run test:smoke (rendered-route assertions incl. /docs/guide/getting-started → "Run a first session") — deferred to CI

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