fix(test): use correct default formats and document .git regression

The webinstall.dev server passes formats=['tar','exe','zip','xz','dmg']
by default — not empty. Fixed Windows UA to use 'Windows' (not
'Windows_NT'). Identified .git source URLs in Go cache as a regression
vs production (not just a priority issue). Updated PROD_NOTES.md with
webinstall.dev serve-releases.js libc bug finding.

PROD_NOTES.md

@@ -54,9 +54,12 @@ The Go cache filters releases more aggressively than the old Node normalize.js:
   `gnu`, so Linux glibc hosts can't match these packages. Fix needed in
   `host-targets.js`: `libc: ['none', 'gnu', 'libc']`. See QUESTIONS.md in the
   Go agent worktree.
-- **ANYOS/ANYARCH .git priority**: Packages like caddy and jq have `.git`
-  source URLs classified as `ANYOS`/`ANYARCH`. The triplet enumeration tries
-  ANYOS before specific OS, so `.git` matches before platform-specific binaries.
+- **Go cache `.git` source URLs (regression)**: The Go cache includes `.git`
+  source repo URLs as release assets. These get classified as
+  `ANYOS`/`ANYARCH` and match before platform-specific binaries because
+  the triplet enumeration tries ANYOS first. Production doesn't have this
+  issue — the old `releases.js` fetchers never included `.git` URLs. Fix:
+  exclude `.git` URLs from Go cache output.
 
 ### Known Pre-existing Issues
 
@@ -66,6 +69,11 @@ The Go cache filters releases more aggressively than the old Node normalize.js:
   "wrong arch" warnings in the build-classifier (armhf vs armv6).
 - **Go illumos/solaris warnings**: Go's illumos and solaris builds trigger
   "wrong os" warnings (expected `sunos`).
+- **webinstall.dev `serve-releases.js` libc bug**: Line 37 calls
+  `UaDetect.arch(req.query.libc)` instead of `UaDetect.libc(...)`. This
+  means the libc query parameter always evaluates to `'error'`, effectively
+  disabling libc filtering in the release API. (Bug is in the webinstall.dev
+  repo, not webi-installers.)
 
 ## Public API Endpoints
 

_webi/test-installer-resolve.js

@@ -49,7 +49,7 @@ let UA_CASES = [
     ua: 'aarch64/unknown Darwin/24.2.0 libc',
     expectOs: 'darwin',
     expectArch: 'aarch64',
-    expectExt: 'tar.gz',
+    expectExt: 'tar.xz',
   },
   {
     label: 'rg macOS arm64',
@@ -159,7 +159,7 @@ async function main() {
         unameAgent: tc.ua,
         projectName: tc.pkg,
         tag: 'stable',
-        formats: [],
+        formats: ['tar', 'exe', 'zip', 'xz', 'dmg'],
         libc: '',
       });