Add Gitea Actions workflow to auto-provision Coder templates

.gitea/workflows/coder-templates.yml pushes every templates/<env>/ dir
to Coder as profiles-<env> on every push to main that touches
templates/**, scripts/**, or profile-templates/** - coder templates push
creates the template on first run and updates it thereafter, so adding a
new templates/<env>/ directory is enough to provision it, no workflow
edits needed.

It also diffs templates/ against the previous commit and runs
`coder templates delete profiles-<env>` for any directory that was
removed. Deletion fails (loudly, as a job warning, not a hard failure)
rather than succeeding if the template still has active workspaces,
since coder templates delete already refuses that server-side.

Runs on the ubuntu-latest self-hosted Gitea runner already registered on
this instance (confirmed via gitea-runner-1's /data/.runner labels) and
installs the coder CLI itself. Needs CODER_URL and CODER_SESSION_TOKEN
as repo/org Actions secrets - documented in README, left for the user to
set up since token creation needs their own Coder login.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -25,15 +25,17 @@ extensions/                 # Agent Skills bundles, installed per env (see below
 Each `templates/<env>/main.tf` is a complete, independent Coder template
 (agent, docker container, code-server, JetBrains). They're deliberately not
 built from a shared Terraform module - only their `locals` block differs
-(which profile file to read). Push them individually:
+(which profile file to read). The naming convention is `profiles-<dir>`
+(matches what `.gitea/workflows/coder-templates.yml` does automatically -
+see below). To push by hand:
 
 ```sh
-coder templates push profiles-default    -d templates/default
-coder templates push profiles-3d         -d templates/3d-printing
-coder templates push profiles-cobol      -d templates/cobol
-coder templates push profiles-python     -d templates/python
-coder templates push profiles-ttrpg      -d templates/ttrpg
-coder templates push profiles-web        -d templates/web
+coder templates push profiles-default      -d templates/default
+coder templates push profiles-3d-printing  -d templates/3d-printing
+coder templates push profiles-cobol        -d templates/cobol
+coder templates push profiles-python       -d templates/python
+coder templates push profiles-ttrpg        -d templates/ttrpg
+coder templates push profiles-web          -d templates/web
 ```
 
 ### How the VS Code profile gets applied
@@ -111,3 +113,40 @@ the `SPECIALTY_SKILLS` env var passed to the script from each template's
 - 3D Printing -> `openscad-parametric`
 - TTRPG -> `foundryvtt-modding` and `ttrpg-lore-weaver`
 - Default / Python / Web -> none (no matching specialty skill exists yet)
+
+### Auto-provisioning (Gitea Actions)
+
+`.gitea/workflows/coder-templates.yml` keeps Coder in sync with this repo on
+every push to `main` that touches `templates/**`, `scripts/**`, or
+`profile-templates/**`:
+
+- **Add** a new `templates/<env>/` directory -> next push creates a new
+  Coder template `profiles-<env>` automatically. No workflow edits needed.
+- **Edit** an existing `templates/<env>/main.tf` (or a shared script/profile
+  it references) -> next push updates that template with a new version.
+- **Remove** a `templates/<env>/` directory -> next push deletes
+  `profiles-<env>` from Coder. `coder templates delete` refuses if the
+  template still has active workspaces, so this fails loudly instead of
+  silently orphaning anyone's running workspace - that failure only shows up
+  as a `::warning::` in the job log, it doesn't fail the whole run.
+
+It runs on the `ubuntu-latest` self-hosted runner already registered on this
+Gitea instance and installs the `coder` CLI itself via `coder.com/install.sh`.
+
+**One-time setup required** (not something this workflow can do for itself -
+needs a human with Coder access):
+
+1. Create a Coder API token - ideally under a dedicated service account
+   rather than a personal login, since this token can create/delete
+   templates:
+   ```sh
+   coder login https://code.octoturge.com
+   coder tokens create --name gitea-ci --lifetime 8760h
+   ```
+2. In Gitea, go to this repo's **Settings -> Actions -> Secrets** (or the
+   org-level equivalent to share across repos) and add:
+   - `CODER_URL` = `https://code.octoturge.com`
+   - `CODER_SESSION_TOKEN` = the token printed by step 1
+
+Until those secrets exist, the workflow will run and fail cleanly at the
+`coder templates push` step rather than doing anything destructive.