Restructure release infra for multiple platforms; migrate real win keys

PyInstaller doesn't cross-compile and TUF metadata filenames aren't
platform-prefixed, so a shared updates/ release and repo tree can't
safely hold more than one OS's build — a second platform's publish
would silently overwrite the first's trust root and metadata.

- scripts/release/repo_init.py, repo_release.py: auto-detect platform
  (win/mac/linux) and operate inside scripts/release/<platform>/ instead
  of a flat scripts/release/ tree.
- labui.spec: bundles root.json from this platform's own tree.
- core/updater.py: points at releases/download/updates-<platform>/
  instead of a single shared updates/ tag.
- Moved the existing real keystore/repository/config (already used for
  a live Windows release) from the old flat path into
  scripts/release/win/ — same keys, same signed metadata, just
  relocated. No new keys generated, existing installs still trust it.
- .gitignore updated for the per-platform paths, plus temporary rules
  covering the old flat path during migration.
- docs/building.md, scripts/release/README.md: rewritten for the
  per-platform flow, including a note that Linux builds should happen
  on Linux/WSL2 (no cross-compiling) and that a bare .exe doesn't
  belong on the updates-<platform> release — only the TUF metadata +
  signed target archive do.

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

1 files changed, 71 insertions, 0 deletions

diff --git a/scripts/release/win/repository/metadata/1.root.json b/scripts/release/win/repository/metadata/1.root.json
new file mode 100755
index 0000000..343b2e2
--- /dev/null
+++ b/scripts/release/win/repository/metadata/1.root.json
@@ -0,0 +1,71 @@
+{
+ "signatures": [
+  {
+   "keyid": "25e91fe88ce247418835d22b18c63a8166038a16b2b9f26f319bc65a8b2687ed",
+   "sig": "cb0c1b0078781b4b87a181deaa03122a7e1f08dd39fab4eac842acd43397e0c5b268009825fa942e86b368b4edd651e69967182981e8be746a60566b42d36109"
+  }
+ ],
+ "signed": {
+  "_type": "root",
+  "consistent_snapshot": false,
+  "expires": "2027-08-01T23:55:23Z",
+  "keys": {
+   "25e91fe88ce247418835d22b18c63a8166038a16b2b9f26f319bc65a8b2687ed": {
+    "keytype": "ed25519",
+    "keyval": {
+     "public": "be8f719618189eb74b524ee92e85eea99a5228fafc7257356b5d8acad2829b24"
+    },
+    "scheme": "ed25519"
+   },
+   "40e5301cd4b92e4a9c2e63dcca99ffa4a5627c25ac6c254f272bb52c9a076cfc": {
+    "keytype": "ed25519",
+    "keyval": {
+     "public": "cbde8cdde12b19b39a786da7128214d01e0f4415e590df34768530fad2bf4702"
+    },
+    "scheme": "ed25519"
+   },
+   "4edf46a4cf08f9b2c59cbe9a435024a8498ce68cc63208f1fbb8b69e74768d42": {
+    "keytype": "ed25519",
+    "keyval": {
+     "public": "1559cdea5a3295593d4c08e6ee625561f7cd96a1dcc0d553b9961734491b801a"
+    },
+    "scheme": "ed25519"
+   },
+   "998b28525eec351c6cdd16d6da3854876e84ab450595feac782ae83d3a8226d6": {
+    "keytype": "ed25519",
+    "keyval": {
+     "public": "6ac7a3b9d83f0d1835ea6fdc0307fe340ea422bc15763fdc0bc197383a61d79b"
+    },
+    "scheme": "ed25519"
+   }
+  },
+  "roles": {
+   "root": {
+    "keyids": [
+     "25e91fe88ce247418835d22b18c63a8166038a16b2b9f26f319bc65a8b2687ed"
+    ],
+    "threshold": 1
+   },
+   "snapshot": {
+    "keyids": [
+     "40e5301cd4b92e4a9c2e63dcca99ffa4a5627c25ac6c254f272bb52c9a076cfc"
+    ],
+    "threshold": 1
+   },
+   "targets": {
+    "keyids": [
+     "998b28525eec351c6cdd16d6da3854876e84ab450595feac782ae83d3a8226d6"
+    ],
+    "threshold": 1
+   },
+   "timestamp": {
+    "keyids": [
+     "4edf46a4cf08f9b2c59cbe9a435024a8498ce68cc63208f1fbb8b69e74768d42"
+    ],
+    "threshold": 1
+   }
+  },
+  "spec_version": "1.0.31",
+  "version": 1
+ }
+}
\ No newline at end of file