feat: signed plugin index with validation and publish pipeline

The catalog the Punktfunk plugin store fetches. Served straight out of this
repository over Gitea's anonymous raw endpoint:

  https://git.unom.io/unom/punktfunk-plugin-index/raw/branch/main/v1/index.json
  https://git.unom.io/unom/punktfunk-plugin-index/raw/branch/main/v1/index.json.sig

Hosts verify the ed25519 signature against a compiled-in public key and only
then parse. Verified that the raw endpoint serves blobs byte-for-byte, which
the signature depends on; .gitattributes pins LF so a Windows checkout cannot
break it from the other direction.

Entries pin one exact version plus that version's registry tarball integrity
hash -- no ranges, no "latest". A plugin author publishing a new version
changes nothing for users; the new version becomes installable only when a
reviewer works the checklist and lands a new pinned entry here. That data
shape is what makes "verified on every release" enforceable rather than a
promise.

Seeded with the two first-party plugins, both integrity hashes confirmed
against the live registry:
  - @punktfunk/plugin-rom-manager 0.3.1 (linux, windows)
  - @punktfunk/plugin-playnite    0.1.1 (windows)

Tooling (bun + TypeScript, node builtins only):
  - validate: every field rule the host enforces, plus a live registry
    cross-check that the pinned version exists and its dist.integrity matches
    the pin. Strict on unknown keys, since the host silently drops entries
    that fail validation -- a `min_host` typo would otherwise ship as a
    missing version floor with no error anywhere.
  - sign / verify / keygen: ed25519 over the exact bytes of index.json.
    keygen never prints the private key; verify defaults to the host-pinned
    public key so an index can be audited with no arguments.

CI splits by trust: pull requests run validate only and hold no secrets, so a
fork PR can never reach the signing key or a token that can write to main.
Publishing from main validates, signs, self-verifies, then commits the
signature back. The loop guard is a paths-ignore filter on v1/index.json.sig,
with a [skip ci] marker as a second line of defence; ed25519 determinism means
an unchanged index re-signs to identical bytes and commits nothing at all.

CI signs after the merge, so there is a brief window where index.json is newer
than its signature. It fails closed -- hosts reject the document and keep
their last good cached catalog -- and is documented as such in the README.

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

v1/index.json

@@ -0,0 +1,49 @@
+{
+  "schema": 1,
+  "name": "unom official",
+  "generated": "2026-07-20T18:00:00Z",
+  "plugins": [
+    {
+      "id": "rom-manager",
+      "pkg": "@punktfunk/plugin-rom-manager",
+      "registry": "https://git.unom.io/api/packages/unom/npm/",
+      "title": "ROM Manager",
+      "description": "Scans your ROM directories, maps them to emulators, fetches box art, and reconciles everything into the host game library as a provider. Includes a console-hosted web UI for mapping and cleanup.",
+      "icon": "gamepad-2",
+      "author": "unom",
+      "homepage": "https://git.unom.io/unom/punktfunk-plugin-rom-manager",
+      "license": "MIT OR Apache-2.0",
+      "version": "0.3.1",
+      "integrity": "sha512-SGqMriqQPOQobXMYiT20w0rcTMNdYfZc8No3fPu57njMN+2eTVBVlQjyn1t3KoRFxfoRYGwuumN4X3aNmS0Tpw==",
+      "verification": {
+        "reviewedAt": "2026-07-20"
+      },
+      "minHost": "0.15.0",
+      "platforms": [
+        "linux",
+        "windows"
+      ]
+    },
+    {
+      "id": "playnite",
+      "pkg": "@punktfunk/plugin-playnite",
+      "registry": "https://git.unom.io/api/packages/unom/npm/",
+      "title": "Playnite",
+      "description": "Bridges your Playnite library on Windows into the host game library, keeping installed games, metadata, and launch commands in sync as a library provider.",
+      "icon": "library",
+      "author": "unom",
+      "homepage": "https://git.unom.io/unom/punktfunk-plugin-playnite",
+      "license": "MIT OR Apache-2.0",
+      "version": "0.1.1",
+      "integrity": "sha512-H40QEcUN7g0wHTy5CFCOTA4+j/FypbVzWSZ0OlW5Ej5+FnnT1fMUDVOx8KEH34mavTy70fd1zx3zDucu9hNQuQ==",
+      "verification": {
+        "reviewedAt": "2026-07-20"
+      },
+      "minHost": "0.15.0",
+      "platforms": [
+        "windows"
+      ]
+    }
+  ],
+  "security": []
+}