chore: bump rmcp 0.12 -> 1.5 + schemars 0.8 -> 1.2

[radiosilence]

Summary

Two bumps that have to travel together — `rmcp` re-exports `schemars`, so a mismatched pair breaks the derive.

`rmcp` 0.12 → 1.5

The 1.0 release added `#[non_exhaustive]` to model structs, so `ServerInfo { ... }` and `Implementation { ... }` struct-literal construction no longer compiles. Rewrote `get_info()` using the builder API that\x27s been there all along:

```rust
let server_info = Implementation::new("fastmail-cli", env!("CARGO_PKG_VERSION"))
.with_title("Fastmail MCP Server")
.with_website_url("https://github.com/radiosilence/fastmail-cli\");

ServerInfo::new(ServerCapabilities::builder().enable_tools().build())
.with_protocol_version(rmcp::model::ProtocolVersion::V_2024_11_05)
.with_server_info(server_info)
.with_instructions(...)
```

Reads cleaner than the old literal form. The proc-macros (`#[tool]`, `#[tool_router]`, `#[tool_handler]`) are unchanged in surface.

`schemars` 0.8 → 1.2

One derive site (`GraphqlRequest`). No API change hits our usage; the `visit` module / `RootSchema` removals don\x27t touch us.

Dead-code warning

Added `#[allow(dead_code)]` on `tool_router: ToolRouter`. The `#[tool_handler]` proc-macro references it in its expansion, but dead-code analysis can\x27t see through the macro — same pattern in rmcp\x27s own tests.

Test plan

• `cargo test` — 89 passing
• `cargo clippy --all-targets -- -D warnings` — clean (including Rust 1.95 lints)
• `cargo fmt -- --check` — clean
• CI green
• Smoke test: `fastmail-cli mcp` starts, Claude Desktop can hit `schema_sdl` and `graphql` tools (MCP integration only verified once deployed — local `cargo test` doesn\x27t cover the stdio transport path)

🤖 Generated with Claude Code