refs #275
The engine-side half of by-name source binding. `SourceSpec` carries a load-bearing
`role: Option<String>` — `Some(name)` for a spec lowered from a bound `Role` (carried
through the blueprint lowering, previously dropped at compile), `None` for a
hand-built raw-index spec. A pure `bind_sources(specs, keyed_supply)` resolves a
`Vec<(role, Box<dyn Source>)>` into the positional `Vec` `run` consumes, in
`SourceSpec` declaration order, erroring named (`SourceBindError`:
Missing/Extra/Duplicate/Unnamed feed) on a mis-bind. `Harness::run_bound` is the
ergonomic method the by-name production path calls.
The raw-index `run(Vec)` primitive and the k-way merge / per-cycle event loop are
untouched: a positional run stays byte-identical (C1, pinned by
`run_bound_out_of_order_matches_positional_run`), and every existing `run(Vec)` caller
keeps working (it ignores `role`). A `BTreeMap` index makes the Duplicate/Extra
diagnostics deterministic.
C4's tie-break guarantee ("source declaration order") is unchanged — `bind_sources`
emits in `SourceSpec` order, so the merge's source-index tie-break resolves on
declaration order regardless of the caller's supply order. The narrow C23 amendment
(a `SourceSpec.role` is load-bearing for source binding, the rest of the flat graph
stays raw-index) is deferred to the ledger note.
The four error-path RED tests assert via `.map(|_| ()).unwrap_err()`: the `Ok` arm
`Vec<Box<dyn Source>>` is not `Debug` (`Source` has no `Debug` supertrait), so a bare
`.unwrap_err()` would not compile — a plan-byte defect corrected here.
Also sweeps the 45 raw-index `SourceSpec { .. }` literals to `SourceSpec::raw(..)`
across the workspace (mechanical, compiler-enumerated) and pins that a bound root
role's name survives lowering.
Verification: `cargo test --workspace` green (0 failed; incl. 5 `bind_sources` cases,
the `run_bound` byte-identity test, the role-survives-lowering pin, and the four
`.sources`-equality twins under the now-stricter `role` equality);
`cargo build --workspace --all-targets` clean; `cargo clippy -p aura-engine
--all-targets` clean.
claude
0b620e1f26