docs(#200): document mint deploy-time source stamping pattern

[fullsend-ai-coder]

Add prescriptive guidance to the Mint function section of AGENTS.md explaining that build metadata for the mint Cloud Function should use deploy-time source stamping rather than runtime environment variables. This prevents metadata from drifting out of sync with the deployed function code.

The paragraph uses aspirational language describing the intended pattern, since the mechanism is not yet fully implemented in the codebase. It guides future agents to choose source stamping over env vars when adding build metadata to the Cloud Function.

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Closes #200

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[fullsend-ai-review]

🤖 Finished Review · ✅ Success · Started 3:25 PM UTC · Completed 3:32 PM UTC
Commit: b776cf6 · View workflow run →

[fullsend-ai-review]

Review — approve

PR: docs(#200): document mint deploy-time source stamping pattern
Scope: 1 file changed (AGENTS.md), +2 lines

Clean documentation addition. The paragraph accurately describes the deploy-time source stamping pattern for the mint Cloud Function and is well-placed in the "Mint function" section of AGENTS.md between the mintcore sync guidance and the dispatch workflows section.

Dimensions reviewed

Dimension	Result
Correctness	✅ Technical claims are accurate — env vars can drift from deployed code (confirmed by UpdateServiceEnvVars in provisioner.go which updates env vars without redeploying). Aspirational language is appropriate since the stamping mechanism is prescriptive guidance.
Security	✅ No secrets, injection patterns, or permission changes.
Intent & coherence	✅ Traces directly to issue #200. Scope matches exactly — single paragraph of prescriptive guidance as authorized. No scope creep.
Style & conventions	✅ Follows the existing **Bold header:** pattern used by sibling paragraphs in the Go code section.
Docs currency	⏭ Skipped — this is a docs-only PR; no code changes to evaluate staleness against.
Cross-repo contracts	⏭ Skipped — no exported APIs modified.

Minor observation (non-blocking)

The example path mintcore/version.go places generated version metadata inside the shared mintcore module rather than at the function source root. Since mintcore is shared with devmint and has .embed sync requirements, a top-level version.go might be a more natural location for mint-specific build metadata. However, the paragraph uses "e.g." to mark this as an example rather than a prescription, and the path matches the upstream implementation referenced in issue #200.

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Verdict: Approve. This is a well-scoped, correctly-placed documentation addition that fills a documented guidance gap (issue #200) to prevent future agents from choosing env vars over source stamping for Cloud Function build metadata.

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Protected files in this PR:

• AGENTS.md