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/component-methods.md

@@ -0,0 +1,65 @@
+# Component Methods / Interfaces — atheos-blog-lxc
+
+**Stage**: INCEPTION — Application Design (minimal depth)
+**Note**: No business logic exists to specify. These are the **contracts between components** —
+the things that must match or the stack silently fails (the classic 502 / permission-denied class).
+
+## I-1 · nginx → php-fpm (the interface most likely to break)
+
+```
+nginx server block:
+  listen 80;
+  root /var/www/atheos;
+  index index.php index.html;
+
+  location = /index.php { fastcgi_pass unix:<FPM_SOCKET>; ... }
+  location ~ \.php$    { fastcgi_pass unix:<FPM_SOCKET>; ... }
+```
+
+**Contract**: `<FPM_SOCKET>` in `nginx.conf` **must equal** the `listen =` path in the php-fpm pool.
+Alpine's `php83-fpm` default differs between packages — resolve it from the installed
+`/etc/php83/php-fpm.d/www.conf` rather than assuming.
+
+- **Input**: HTTP request; **Output**: `text/html` from the PHP process
+- **Failure mode if mismatched**: `502 Bad Gateway` (socket missing) — AC-2 fails
+
+## I-2 · Atheos → filesystem (the write contract)
+
+Atheos's installer requires **write access** to exactly these paths, relative to `/var/www/atheos`:
+
+| Path | Why | Mode |
+|---|---|---|
+| `config.php` | installer writes the config; file must exist | writable by FPM user |
+| `data/` | user accounts, settings | writable |
+| `workspace/` | projects (incl. the `blog` clone) | writable |
+| `plugins/` | plugin install/marketplace | writable |
+| `themes/` | theme install | writable |
+
+- **Owner/group**: the php-fpm run user (resolved from the pool config)
+- **Failure mode**: installer shows a dependency error; AC-3 fails
+
+## I-3 · Atheos (`codegit`) → git CLI
+
+- **Requires**: `git` on `PATH`
+- **Requires**: `safe.directory` for the workspace — otherwise git refuses with
+  `detected dubious ownership` because the FPM user differs from the filesystem owner
+- **Identity**: `user.name` / `user.email` are **deliberately UNSET** (design Q1=B).
+  The operator sets them first thing after SSH (see RUNBOOK).
+- **Failure mode**: "dubious ownership" errors, or commit refused for missing identity
+
+## I-4 · git CLI → Gitea
+
+- **Remote (initial)**: `https://git.aridgwayweb.com/armistace/blog.git` (public ⇒ no credential)
+- **Remote (operator, later)**: `git@git.aridgwayweb.com:armistace/blog.git` — the RUNBOOK gives the
+  exact `git remote set-url` command for after the key is added
+- **Contract**: the agent must **not** alter the remote to SSH itself (FR-6/FR-11)
+
+## I-5 · OpenRC service contract (not systemd)
+
+| Service | Enable | Purpose |
+|---|---|---|
+| `nginx` | `rc-update add nginx default` | HTTP |
+| `php-fpm83` | `rc-update add php-fpm83 default` | FastCGI (verify exact rc name on 3.23) |
+
+- **Failure mode if not enabled**: works until first reboot, then AC-6 fails. This is why NFR-2 is
+  verified with an actual reboot rather than a service-status check.