[FEATURE] Adopt rmcp 3.3.0 for MCP initialize negotiation

[puretensor]

Seat: grok-4.6 / xhigh (adversarial review wave 5, 2026-09-11)
Category: [FEATURE]

Problem / Opportunity: pTask's MCP server (/mcp and pt mcp) is every HAL session's task surface. It pins rmcp 3.2.0 (2026-08-31). rmcp 3.3.0 shipped 2026-09-10 and extracted protocol-version negotiation out of the default initialize body into ServerHandler::negotiate_initialize (modelcontextprotocol/rust-sdk#1247). The default initialize now calls that method. Staying on 3.2.0 means pTask's handshake does not take the path the SDK now documents as the negotiation rule.

Evidence:

crates.io (fetched 2026-09-11):

id rmcp
max_version 3.3.0
newest 3.3.0
updated 2026-09-10T15:32:23.420168Z
3.3.0 2026-09-10T15:32:23.420168Z yanked=False
3.2.0 2026-08-31T23:16:49.374902Z yanked=False

Changelog (https://github.com/modelcontextprotocol/rust-sdk/blob/rmcp-v3.3.0/crates/rmcp/CHANGELOG.md):

## 3.3.0 - 2026-09-10
### Added
- add ServerHandler::negotiate_initialize (#1247)

SDK source on the 3.3.0 tag (https://raw.githubusercontent.com/modelcontextprotocol/rust-sdk/rmcp-v3.3.0/crates/rmcp/src/handler/server.rs): the default initialize is now set_peer_info plus self.negotiate_initialize(&request). Quote from the method docs: "This is the whole body of the default initialize minus its set_peer_info side effect, so a server that overrides initialize to add its own can call this instead of restating the negotiation rule."

RED — same test injected on an origin/main worktree still pinned to rmcp 3.2.0:

error[E0599]: no method named `negotiate_initialize` found for struct `mcp::PtaskMcp` in the current scope
   --> crates/ptask-server/src/mcp.rs:626:14
help: there is a method `initialize` with a similar name
   --> rmcp-3.2.0/src/handler/server.rs:318:9
error: could not compile `ptask-server` (lib test) due to 1 previous error

Change: Pin rmcp = "3.3.0" (workspace dep; lockfile also moves rmcp-macros 3.2.0 → 3.3.0). Workspace SemVer 3.28.1 → 3.29.0 (MINOR; Lane 1). Add negotiate_initialize_advertises_tools_on_a_supported_protocol so the new API is called on PtaskMcp and the tools capability plus negotiated protocol version are asserted. Lockfile churn is 22 lines (rmcp + macros + workspace crate stamps). No hmac/sha2/reqwest major bumps — those stay optional behind rmcp features we do not enable.

Verification:

$ cargo test --locked --offline -p ptask-server negotiate_initialize_advertises_tools -- --nocapture
test mcp::tests::negotiate_initialize_advertises_tools_on_a_supported_protocol ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 59 filtered out

$ bash scripts/ci-version-check.sh
version-check: workspace, lockfile, internal requirements, and manpage agree on 3.29.0

$ bash scripts/generated-artifacts.sh --check
generated-artifacts: checked-in files match the CLI

$ cargo fmt --all -- --check   # clean
$ cargo clippy --workspace --all-targets --locked -- -D warnings   # Finished
$ bash scripts/ci-production-build-check.sh
production-build-check: release and fallback builds enable native-ml

$ cargo test --workspace --locked --offline
ptask_bot     14 passed
pt             31 passed
ptask_core    262 passed
ptask_distill  26 passed + 7 integration
ptask_notify    3 passed
ptask_server   60 passed
ptask_tui       2 passed

Risk & rollback: pTask does not override initialize; it picks up the 3.3.0 default (initialize → negotiate_initialize). The new test locks the tools advertisement and that the negotiated version is in supported_protocol_versions(). Revert is a clean single-commit revert. Reviewer restacks SemVer from main (3.28.1).