fix(supervisor): reject MCP initialize batches

[shiju-nv]

Summary

Reject an MCP initialize request when it appears in a JSON-RPC batch. Initialization is a standalone bootstrap exchange, so allowing it in a batch would make later profile selection ambiguous before policy evaluation can authorize or forward any member.

Related Issue

Related to #2174. This is one small fail-closed prerequisite and does not close the roadmap issue.

Changes

• Reject MCP-mode batched initialize calls before policy evaluation.
• Preserve generic JSON-RPC batch handling, including a generic initialize method, unchanged.
• Add focused parser regressions for both behaviors.

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (if applicable)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

[johntmyers]

gator-agent

PR Review Status

This focused fail-closed change is project-valid under accepted issue #2174. The initial code review found no blocking issues: MCP batches containing initialize are rejected before policy evaluation, generic JSON-RPC batch behavior remains unchanged, and focused parser regressions cover both paths.

Blocking findings:

• No blocking findings remain

Carried findings:

• None

Non-blocking suggestions:

• None

Gator metadata

• Validation: Focused supervisor-network prerequisite for accepted issue #2174
• Docs: Not needed; this is internal protocol enforcement with no direct user-facing UX change
• Checks: Current branch, DCO, vouch, and Helm gates are green; required E2E dispatch is being reconciled
• E2E: test:e2e required for network-proxy policy enforcement
• Head SHA: ecacd8d211223caca29dcdc0c96908093e478533
• Base SHA: d7cb6e456db0dab6742d29dfca32bf9056be94cf
• Merge base SHA: c93b2fa7da3a40a6dd6c077973cb13d2755f7e50
• Patch ID: a98e7fb797d5a1086ad9a5382417dfe9738bd7be
• Gator payload: 8
• Review mode: initial
• Previous reviewed SHA: none
• Review budget exhausted: no
• Maintainer decision required: no
• Next state: gator:in-review

[github-actions]

Label test:e2e applied for ecacd8d. Open the existing run and click Re-run all jobs to execute with the label set. The run will execute the standard E2E suite after building the required gateway and supervisor images once. The matching required CI gate status on this PR will flip green automatically once the run finishes.

[johntmyers]

gator-agent

Monitoring Complete

Monitoring is complete because this PR has merged.

Final status: Gator review found no blocking issues, the required test:e2e suite passed, required checks were green, and maintainer approval was present before merge.

I removed the active gator:* label because there is nothing left for gator to monitor on this PR.

Gator metadata

• Head SHA: ecacd8d211223caca29dcdc0c96908093e478533
• Gator payload: 8
• Previous state: gator:merge-ready
• Final state: merged