ci(dupe): ts_emit.t27 and verilog_emit.t27 share 18 helper bodies; move them into one t27b module #10058

Problem

The Duplicate Body Ratchet (python3 tools/dupe_scan.py, CI check duplicate-bodies) has been red on master since d03afb0 (#10047). It was green at 60d332d.

#10047 added specs/tri/t27b/ts_emit.t27, and 18 of its function bodies repeat bodies in specs/tri/t27b/verilog_emit.t27:

child_holding, dec_len, holds, in_scope, line_near, param_index, param_name_hi, param_name_lo, parent_of, put_bytes, put_dec, put_ind, resolve, sym_at, sym_of, tmeta, tnode, to_front.

Every open PR inherits the red check (seen on #10053).

Repair

Not a bless. t27c splices used modules selectively (bootstrap/src/use_resolve.rs: only referenced names, each module once per import closure), and both emitters already reach cli/t27b only through t27c gen-rust. So the shared helpers can live in one module that both emitters use:

• new specs/tri/t27b/emit_core.t27 (module T27bEmitCore, use tri::t27b::verilog_plan;): the refusal room and symbol constants, the 15 byte/name/scope helpers, and the three tree fixtures (tnode, tmeta, holds), with its own tests;
• ts_emit.t27 and verilog_emit.t27 drop their copies and use tri::t27b::emit_core;;
• regenerate gen/rust/tri/t27b/{ts_emit,verilog_emit}.rs, reseal the edited specs, seal the new one, and add the ledger row for the new spec.

Done when

• python3 tools/dupe_scan.py exits 0 with no ledger change;
• t27b verilog and t27b ts write the same bytes before and after on the same inputs;
• the specs are sealed (no new seal debt).