RING-00: the decision core in T27, generating valid Rust

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Part of #1279. Ring 0 — the decision core: everything the Queen decides from numbers already in hand. No clock, no network, no store, no strings.

A draft is already in the tree and generates Rust, but not valid Rust: the backend emits V.a where Rust needs V::a, and a switch used as a function body collapses to an empty match. Working around this by hand-writing Rust is forbidden. Work around it with the subset the backend lowers correctly: comparison with ==, if/else, and returning a qualified name.

The compiler itself belongs to another agent's repository. Do not edit it.

Done when

• t27c gen-rust rings/T27-00/queen_core.t27 produces Rust that compiles under rustc --crate-type lib with no errors.
• The module is named: generated Verilog is called queen_core, not unknown.
• Four decisions are covered: retry, review, merge gate, capacity.
• No floating point anywhere in the ring.

Boundary

rings/T27-00/queen_core.t27

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Done. The ring-00 source is in the tree at rings/T27-00/queen_core.t27 and generates Rust that compiles under bare rustc --crate-type lib.

The bee chose integer constants over enums and said why in the file itself: the seed compiler's enum shorthand emitted variant::, switch arms were dropped, and the enum derives dragged serde into code that must compile standalone. Two of those three are now fixed in the seed (t27#2247), so the constants can become an enum when that lands.

Correction to the record. This task was marked accepted with committedFiles: 1 while its branch did not exist. The count came from the shared checkout, not from a commit, because the bee had been dispatched with a task struct copied before its worktree was prepared. Both defects are fixed: the dispatcher re-reads the registry, and acceptance now requires a commit it can name.