Retire the Crucible container image

Nothing consumes registry.westgate.pw/deployment/crucible: prod.yml no
longer reserves a slot for it and no runtime or recovery path pulls it.
Binaries, wrappers, and the Nix input are the supported ways to run
Crucible. Delete the image workflows (build/publish/test), the
Dockerfile, and the make image target; update docs to match.

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

AGENTS.md

@@ -41,13 +41,14 @@ section and `.gitea/workflows/`.
 - Dev loop: `nix develop`, then `make check` / `make build` / `make smoke`
   (see Commands below).
 - Release: push a `v*` tag. CI uploads cross-built binaries + wrappers to the
-  Gitea release and publishes the `crucible` container image.
+  Gitea release. There is no container image; Crucible ships as binaries,
+  wrappers, and the Nix input.
 - Consumers (they download released binaries via the wrapper; they never
   vendor a toolkit):
   - sow-module — https://git.westgate.pw/ShadowsOverWestgate/sow-module
   - sow-topdata — https://git.westgate.pw/ShadowsOverWestgate/sow-topdata
   - sow-assets-manifest — https://git.westgate.pw/ShadowsOverWestgate/sow-assets-manifest
-  - sow-platform (deploys the released image/pins) —
+  - sow-platform (infra/deploy authority) —
     https://git.westgate.pw/ShadowsOverWestgate/sow-platform
 
 ## What this repo owns / does not own
@@ -62,7 +63,7 @@ is `sow-platform`).
 
 1. **Fail closed, never fake.** A builder with no migrated logic yet (`depot`)
    exits `70`. Do not stub a builder to emit a placeholder artifact.
-2. **Binaries are not committed.** They are CI artifacts / image layers.
+2. **Binaries are not committed.** They are CI artifacts.
    `/bin/`, `*.exe`, `nwn-tool`, `sow-toolkit` are gitignored.
 3. **The registry is the command surface.** `internal/dispatch.Registry` is the
    single source of truth; keep it in sync with `cmd/` and
@@ -81,7 +82,6 @@ is `sow-platform`).
 nix develop && make check   # vet + test + shellcheck + yamllint
 make build                  # cmd/* -> ./bin
 make smoke                  # assert fail-closed contract
-make image                  # crucible:<sha>
 ```
 
 ## Tests