chore(deps): bump rmcp from 2.2.0 to 3.1.2

[dependabot]

Bumps rmcp from 2.2.0 to 3.1.2.

Release notes

Sourced from rmcp's releases.

rmcp-macros-v3.1.2

Fixed

• emit cache hints from handler macros (#1120)

Other

• upgrade darling and syn (#1138)

rmcp-v3.1.2

Fixed

• (auth) map 401/403 challenges on the SSE GET stream (#1152)
• (sse) loop instead of recursing when skipping SSE events (#1146)
• (auth) preserve issuer trailing slash during discovery (#1145)

rmcp-macros-v3.1.1

Fixed

• emit cache hints from handler macros (#1120)

Other

• upgrade darling and syn (#1138)

rmcp-v3.1.1

Fixed

• emit cache hints from handler macros (#1120)
• expose MRTR state to tool handlers (#1104)
• disambiguate input-required results (#1103)

Other

• make async-trait optional (#1119)

rmcp-macros-v3.1.0

Added

• add strict stateless protocol metadata validation (#1091)

Other

• document the ping utility with examples (#1106)
• complete Tier 1 feature docs and finalize roadmap (#1101)
• (conformance) meeting requirements for tier 1 (#1087)

rmcp-v3.1.0

Added

... (truncated)

Commits

• 02c62ae chore: release v3.1.2 (#1148)
• c345078 fix(auth): map 401/403 challenges on the SSE GET stream (#1152)
• f8e6382 chore(deps): bump taiki-e/install-action from 2.85.7 to 2.85.8 (#1153)
• 8fb3e04 chore(deps): bump github/codeql-action from 4.37.4 to 4.37.6 (#1154)
• 3c8fb2a fix(sse): loop instead of recursing when skipping SSE events (#1146)
• e150d4f fix(auth): preserve issuer trailing slash during discovery (#1145)
• 9a3168a chore(deps): bump taiki-e/install-action from 2.85.6 to 2.85.7 (#1139)
• baac607 chore: release v3.1.1 (#1115)
• f57d585 chore: upgrade darling and syn (#1138)
• 07bcda2 fix: emit cache hints from handler macros (#1120)
• Additional commits viewable in compare view

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[pacharanero]

Dependency review

Closing rather than merging this bump.

• The MCP feature does not compile on rmcp 3.1.2: ListToolsResult gained cache/result metadata and ServerHandler::call_tool now returns CallToolResponse. The required CI job is correctly red.
• 3.1.2 is superseded by stable 3.1.3, so this lockfile no longer validates the latest release permitted by the manifest.
• More importantly, neither 3.1.2 nor 3.1.3 meets this repository's MCP adoption gate. The official SDK's stdio reader still has an unbounded line buffer: rust-sdk#1030 and proposed fix #1049 are both still open as of 2026-08-19. The built-in service also needs aggregate-request/unread-output backpressure review.
• Accepting the major migration safely would therefore require a custom bounded transport, overload/backpressure handling, API migration, and real-process protocol conformance tests. There is no concrete need to carry that local fork while the upstream fix is active.

A new bump should be reviewed once a stable rmcp release includes the bounded-reader fix. At that point it should migrate the 3.x response APIs and validate modern server/discover, legacy initialization, frame limits, overload, and stdout backpressure with real-process tests.

The existing optional rmcp 2.2.0 path has the same upstream transport limitation; closing this PR avoids claiming the 3.x migration is safe, but does not by itself remediate that existing risk.

[dependabot]

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If you change your mind, just re-open this PR and I'll resolve any conflicts on it.