feat: provision Alpine LXC 136 running Atheos, wired to Gitea

Provisions a LAN-only browser code editor (Atheos) in an Alpine 3.23 LXC on the
scotty PVE node, with armistace/blog cloned and ready to edit. Built via the
AI-DLC workflow; the full process trail is in aidlc-docs/.

Deliverables
- scripts/provision.sh          rebuild the guest from scratch (re-runnable)
- scripts/update-atheos.sh      move Atheos to latest upstream and RE-PIN
- scripts/build-and-test.sh     captures evidence for every acceptance criterion
- files/atheos.conf             nginx vhost (socket path byte-matches the FPM pool)
- files/ssh-config              ~atheos/.ssh/config deploy-key alias
- RUNBOOK.md                    operational guide (START AT STEP 1)
- docs/security-notes.md        credential model + wider-web hardening TODOs
- docs/resiliency-notes.md      what a non-PoC deployment would need

Design decisions
- D1 no git identity is configured by the agent; the operator sets it. Git will
  refuse the first commit until then, which is deliberate (requirement FR-11).
- D2 Atheos pinned to commit f90cd18 (build 611) with a verified tarball sha256,
  plus update-atheos.sh as the deliberate escape hatch.
- D3 nginx :80, web root /var/www/atheos, php-fpm over a unix socket.
- D6 git auth is a per-repository DEPLOY KEY scoped to armistace/blog, not a
  personal access token (a PAT's write:repository scope reaches every repo the
  account can write).

Verified on the live guest (40 checks, 0 failures)
- AC-2  Atheos served over HTTP 200 by nginx+php-fpm; socket paths byte-match
- AC-3  20 posts + themes/cleanblog present; owned by the php-fpm user
- AC-4  all five writable paths writable as the service user
- AC-5  remote targets armistace/blog; deploy key authenticates over SSH
- AC-6  survival proven with a real container restart, marker byte-identical
- AC-8  no python/pelican/pip/make and no DB engine - scope boundary enforced
- FR-11 git identity is empty; deploy key mode 600 owned by the service user

Traps documented in the RUNBOOK (each cost real debugging time)
- The Gitea SSH user is `gitea`, NOT `git` (app.ini SSH_USER=gitea). With `git`,
  sshd answers "Invalid user git" and rejects before reading authorized_keys,
  which is indistinguishable from a bad key.
- The Gitea SSH endpoint is the LAN address (:22 is not forwarded publicly).
- `uptime` and `free` report the PVE HOST inside an LXC without lxcfs, so a
  container that just restarted can claim days of uptime.

aidlc-docs/design-artifacts/components.md

@@ -0,0 +1,33 @@
+# Components — atheos-blog-lxc
+
+**Stage**: INCEPTION — Application Design (minimal depth)
+**Note**: This project has no application code to design. "Components" here are the **runtime
+pieces of the provisioned guest and their interfaces**, recorded so unit boundaries are defensible
+and a later agent inherits the map.
+
+## Provisioned by the agent
+
+| ID | Component | Purpose | Responsibilities |
+|---|---|---|---|
+| **C1** | **LXC guest** (`136` on scotty, Alpine 3.23) | The isolated runtime | OpenRC init, network (`eth0`, DHCP/static), 20 GB rootfs, timezone |
+| **C2** | **nginx** | HTTP front end | Listen `:80`; serve static assets; dispatch `*.php` to C3 over a unix socket |
+| **C3** | **php-fpm (`php83`)** | PHP FastCGI runtime | Execute Atheos PHP as a dedicated unprivileged user; extensions ZIP/OPENSSL/MBSTRING; `allow_url_fopen=On` |
+| **C4** | **Atheos** (upstream PHP app, pinned SHA) | The browser editor | File tree, editor, and git operations via its `codegit` component |
+| **C5** | **Atheos workspace** (`/var/www/atheos/workspace`) | Project storage | Holds working copies Atheos opens as projects; must be writable by C3 |
+| **C6** | **git CLI** | VCS client | Invoked by C4's `codegit`; needs `safe.directory`, has **no configured identity** (operator sets it) |
+| **C7** | **`blog` working copy** | The thing the operator edits | A clone of `armistace/blog` at `C5/blog`, on `master` |
+
+## External / not provisioned by the agent
+
+| ID | Component | Relationship |
+|---|---|---|
+| **C8** | **Gitea** (`git.aridgwayweb.com` → LXC 109, .155) | Clone source. **Read-only** from this project's perspective — the agent never pushes |
+| **C9** | **Operator (human)** | SSHes in; **owns**: SSH key, git identity, Atheos admin account, and switching the remote to SSH |
+
+## Explicit non-components (scope guards)
+
+- **No database.** Atheos is file-backed; nothing is installed for it.
+- **No Python / pelican / `make html`.** The build pipeline is out of scope (FR-1 / AC-8). The
+  presence of Python would be a **defect**, not a bonus.
+- **No NPM proxy host, no DNS, no port-forward** (LAN-only, FR-10).
+- **No Atheos user seeded by the agent** — C9 creates the first account via the installer.