* fix(security): correct XML double-unescape and non-CSPRNG nonce from CodeQL sweep
Two real defects surfaced by the 2026-08-12 code-scanning triage.
decodeXmlText decoded `&` before `"`/`'`, so `"` — the encoding of
the literal text `"` — collapsed to `"` in a second pass. The decoded values feed the
workspace-root trust comparison in parseTrustedCodexEnvironment, so an encoded path could
decode into a different path than the client declared. Decoding `&` last fixes it.
The tinycms nonce fell back to `Date.now()` plus a non-cryptographic PRNG when
`crypto.randomUUID` was absent. That nonce is signed into the provider's anti-replay
payload, so the fallback produced a predictable value silently. It is now always
`randomUUID()` from node:crypto, which is present on every supported runtime.
Both guards are mutation-validated: reverting either fix makes the new test fail.
Refs #9985
* fix(security): reword tinycms nonce comment so the CSPRNG regression test holds
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Co-authored-by: backryun <bakryun0718@proton.me>
