Fix Quartz build to preserve git history for accurate file dates (#105)

## Summary

Fixes the "isn't yet tracked by git, dates will be inaccurate" warnings in the Build docs step by restructuring how Quartz builds the documentation.

## Problem

Previously, we copied docs into Quartz's content folder. Since this was inside a fresh Quartz clone with no history of our files, the `CreatedModifiedDate` plugin couldn't determine accurate dates.

## Solution

Build Quartz from within the blumeops repo instead:
1. Copy Quartz's build system (quartz/, package.json, etc.) into the workspace
2. Symlink `content` -> `docs` (preserves git history)
3. Symlink `docs/CHANGELOG.md` -> `../CHANGELOG.md`
4. Build from workspace root where git can trace file history
5. Clean up artifacts after creating tarball

## Deployment and Testing

- [ ] Run build workflow and verify no "not tracked by git" warnings
- [ ] Verify file dates appear correctly on built docs site

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/105

docs/how-to/update-documentation.md

@@ -56,7 +56,7 @@ Fragments are automatically collected into `CHANGELOG.md` (at repo root) during
 | `bugfix` | `bugfix/` | Bug fixes |
 | `infra` | `infra/` | Infrastructure changes |
 | `doc` | `doc/` | Documentation updates |
-| `misc` | `misc/` | Other (content hidden in changelog) |
+| `misc` | `misc/` | Other changes |
 
 ## Runner Environment