remove origin validation

ALLOW_ANY_ORIGIN, ALLOW_ANY_ORIGIN_MUSIC, and everything they gated. The flag
defaulted to ON, so none of it ran on a real install — what comes out is
documented defence in depth that was already switched off. The file said so
itself: "Both flags and their call sites come out once the tailnet is the
perimeter."

Origin was never authentication here in any case. An app's `officer://<hex>`
origin is chosen by the client, forgeable outside a browser, and extractable from
a shipped binary.

Gone: the two flags, isOriginAllowed, isOriginCheckDisabled, isMusicOriginExempt,
originValidationMiddleware, ORIGIN_RULES and the whole OFFICER_<APP>_ORIGIN
scheme, PUBLIC_URL's origin/host derivation, and origin-validation.test.ts, which
existed only to pin them. CORS now echoes whatever Origin it is given, which is
what every install already did.

What SURVIVES is the reason this needed care. origin-validation.ts held two
unrelated things, and the second was the global authorization gate — a valid
non-owner token reaches only what its role grants, deliberately NOT under the
flag because it is account-based rather than origin-based. Its own comment called
it "the airtight half". Deleting the file wholesale would have deleted
authorization.

So it moves to _middlewares/capability-gate.ts as capabilityGateMiddleware, with
the name matching what it does: nothing in it reads an Origin header any more.
hono.ts mounts it in the same position, ahead of every router.

origin-middleware.ts stays and is untouched — it extracts the Origin for six auth
handlers that log it, and for passkeys. Extraction, not validation.

Also updates every claim that rested on the old model: CLAUDE.md's security
section and repo map, docs/secret-store.md, docs/mobile-api-keys.md, and five
messages in machine-setup's Tailscale section which told the owner to set
ALLOW_ANY_ORIGIN=false when declining a tailnet. That advice is now impossible to
follow, and the honest version is different: with no tailnet the token is the
whole lock, so put a proxy in front and restrict who can reach it.

Not typechecked (empty node_modules, frozen installs). Every changed file parses;
the setup section was run and writes four variables now.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.env.example

@@ -30,11 +30,6 @@ VAULT_STORE_KEY="<generate with: openssl rand -base64 32>"
 # only loads this file, so `bun dev` against a production .env runs fully hardened.
 # PUBLIC_BUILD_ENV=dev
 
-# Origin checking is OFF unless this is explicitly "false" — an inversion of the usual rule, and one
-# that is only defensible when the tailnet is the perimeter. On a machine with no tailnet, set it to
-# false. Written explicitly rather than left to the default so the choice is visible.
-ALLOW_ANY_ORIGIN=true
-
 # DATA_PATH, OFFICER_ITEMS_DIR and HOME_DIR were here until 2026-08-12 and are no longer read.
 # The install root is derived as the parent of the working directory (src/servers/data-path.ts), so
 # data/, capabilities/ and dockers/ follow from it; the owner's home comes from the OS. Three values