docs(local): update install guidance — `glab orbit local` ships today (drop "must build from source")
## Problem
Three user-facing docs say "Until packaged binaries ship, you must build from source" — but `glab orbit local --install --yes` already ships the managed `orbit` binary (v0.58.0 as of this writing). The wrapper is in `glab` 1.94.0+.
Verified:
```bash
glab --version
# glab 1.97.0 (3804f048)
glab orbit local --install --yes
# Downloading orbit-local-linux-x86_64.tar.gz version 0.58.0...
# ✓ Checksum verified
# ✓ Installed to: /home/dgruzd/.config/glab-cli/bin/orbit
```
Stale guidance lives in:
- `docs/source/local/getting-started.md` (lines 23–25 + the "60-second quickstart" note line 43–46 marks `glab orbit local` as "the planned packaging path")
- `docs/source/local/access/cli.md` (line 27 — the build-from-source `mise install && mise run build:cli` flow is presented as the only install path)
- `docs/source/local/access/glab.md` (top-of-page note line 30–33 — "Both `glab orbit local` and `glab orbit setup` are planned for a future glab release")
## Proposed solution
Rewrite each page so that **`glab orbit local`** is the **primary** install path, and build-from-source is demoted to a "for contributors" note.
Suggested content for each:
### `docs/source/local/getting-started.md`
Replace the note block with:
```markdown
> [!note]
> Orbit Local is experimental. The current install path is `glab orbit local`
> (in `glab` 1.94 or later); the binary downloads on first use.
```
And rewrite the 60-second quickstart to use `glab orbit local index <path>` as a verified, working command (not "planned").
### `docs/source/local/access/cli.md`
Add a new "Install" section that leads with `glab orbit local --install --yes` and keeps the `mise run build:cli` flow only for "Contributing to Orbit".
### `docs/source/local/access/glab.md`
Rewrite the page so the top half describes commands that **already work** (`glab orbit local index`, `glab orbit local query -`, `glab orbit local schema`) and the bottom half clearly marks `glab orbit setup`, `glab orbit local mcp serve`, and `glab orbit local status` as **planned** with linked issues.
## Affected files
- `docs/source/local/getting-started.md`
- `docs/source/local/access/cli.md`
- `docs/source/local/access/glab.md`
(Optional touch-up: `docs/source/local/_index.md` — line 46 "Drive Orbit Local through `glab orbit local` (planned)" should drop "planned".)
## Validation
```bash
mise run lint:docs
# Sanity check that the documented commands actually run:
glab orbit local --install --yes
glab orbit local index /any/repo
echo '{"query_type":"traversal","node":{"id":"d","entity":"Definition","filters":{"name":{"op":"eq","value":"main"}}},"limit":1}' \
| glab orbit local query -
```
## Related
- This is split from a larger UX audit (docs say "planned" for commands that ship, and "ships" for commands that don't exist).
- The `mcp serve` parts of `glab.md` are tracked as a roadmap item — leave them as "planned" in this MR.
## Hackathon notes
- **Difficulty:** L0
- **Estimated effort:** 1–2h
- **No server needed:** Yes
- **Prerequisites:** none — pure docs editing
issue