Audit response: fix BL-16 through BL-20 and the low findings, same day

BL-16 (high): a remote signer's auth_url is attacker-controlled input that
became a clickable href. sanitizeAuthUrl in core now admits only https
(or loopback http) -- javascript:/data:/blob:/custom schemes are dropped
without consuming the surfacing slot -- and the widget link shows the
hostname. Hostile-scheme tests at both layers.

BL-17: the post-creation PRF fallback assertion is pinned via
allowCredentials to the credential that was just created, so a multi-
passkey account sheet can no longer silently bind an older passkey's
account.

BL-18: queryOnce's timeout path sent CLOSE before settling, unguarded --
a relay dying mid-query stranded the promise and everything queued behind
the worker's serial queue. The send is guarded; settling is unconditional.
MockRelay.close() now terminates live sockets (it previously waited on
them forever), and a suppressEose switch models the silent relay.

BL-19: relays are no longer trusted to honor limits. Buffered queries
enforce filter.limit locally, drop replayed duplicate ids, and cap at
1000 events; a 20-copy replay now yields one event.

BL-20: the .semgrep.yml try/catch fallback pattern never parsed, so the
entropy rules silently did not run. Rewritten in parseable form and
verified under the pinned Semgrep 1.171.0: fires on hostile code, exits
0 on the clean tree.

Lows: NIP-07 and NIP-46 verify returned signed events (signature, pinned
session identity, field equality with the request); Nip46Client.close()
wipes the client and conversation keys (§11.10); passkey labels carry a
short suffix so multiple accounts are distinguishable; postcss bumped to
8.5.25 (GHSA-fxqj-rqcc-2cmp); GitHub Actions pinned to commit SHAs.
Deferred as interop (recorded in TODO): NIP-46 protocol logout and
switch_relays. 12 new adversarial tests; 256 total.

Co-Authored-By: Claude Fable 5 <[email protected]>

.github/workflows/security.yml

@@ -14,10 +14,10 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 25
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
           persist-credentials: false
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
         with:
           node-version: 22
           cache: npm
@@ -30,7 +30,7 @@ jobs:
           mkdir -p security-artifacts
           npm sbom --sbom-format cyclonedx > security-artifacts/sbom.cdx.json
           find packages/widget/dist packages/demo/dist -type f -print0 | sort -z | xargs -0 sha256sum > security-artifacts/SHA256SUMS
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
           name: bitlogin-security-artifacts
           path: security-artifacts/
@@ -40,7 +40,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 20
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
           persist-credentials: false
           fetch-depth: 0
@@ -51,6 +51,6 @@ jobs:
       - name: Enforce local randomness rules (entropy audit §13)
         run: semgrep scan --config .semgrep.yml --error --timeout 0 packages
       - name: Scan repository history for secrets
-        uses: gitleaks/gitleaks-action@v2
+        uses: gitleaks/gitleaks-action@ff98106e4c7b2bc287b24eaf42907196329070c7 # v2
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}