Review exploring-the-docs and add doc consistency checks (#112)

## Summary
- Reviewed and cleaned up exploring-the-docs tutorial: simplified wiki-links, fixed broken replication/ reference, added Related section, corrected zk-docs flags to match CLAUDE.md
- Added orphan detection to doc-links (finds docs not linked from any other doc)
- Added new doc tooling: `doc-index` (checks category index coverage), `doc-stale` (staleness report), `doc-tags` (tag inventory)
- Added `doc-index` as a pre-commit hook
- Updated use-pypi-proxy to document env-var-based proxy toggle for pip/uv
- Updated ai-assistance-guide with new doc task descriptions

## Test plan
- [ ] Run `mise run doc-links` — passes
- [ ] Run `mise run doc-index` — passes
- [ ] Run `mise run doc-stale` — informational output
- [ ] Run `mise run doc-tags` — informational output
- [ ] Pre-commit hooks pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/112

docs/tutorials/ai-assistance-guide.md

@@ -94,9 +94,12 @@ BlumeOps operations are driven by mise tasks. Run `mise tasks` to list all avail
 | `dns-up` | Apply DNS changes via Pulumi |
 | `tailnet-preview` | Preview Tailscale ACL changes |
 | `tailnet-up` | Apply Tailscale ACL changes via Pulumi |
-| `doc-links` | Validate wiki-links in documentation |
+| `doc-links` | Validate wiki-links in documentation (includes orphan detection) |
+| `doc-index` | Check every doc is referenced in its category index |
 | `doc-titles` | Check for duplicate doc titles |
 | `doc-filenames` | Check for duplicate doc filenames |
+| `doc-stale` | Report docs by last-modified date, highlight stale ones |
+| `doc-tags` | Print frontmatter tag inventory across all docs |
 | `doc-random` | Select a random doc card for review |
 | `indri-runner-logs` | View Forgejo workflow logs from local runner |