Per mara's review on #2896: has_log: bool was fully redundant once
build_log_id: Option<i64> existed alongside it (has_log was always
just build_log_id.is_some()). Dropped has_log, threading the single
Option<i64> field through job_queue::mod.rs, the hivectl NodeView
test-helper literal, and the one remaining frontend consumer
(findLiveBuild's live-log-panel gate, which now checks
build_log_id != null instead of the separate bool).
Also fixed a now-stale doc comment on GET /api/build-log/{node_id}
that claimed the dashboard used on-demand node-id fetches "instead
of an inline build_log_id on the wire" -- no longer true after this
PR put one there for the BUILD L0GS deep-link.
cargo build/clippy/test clean across the three touched crates; nix
fmt clean; frontend build verified (0 has_log references, 3
build_log_id references in the built builds.js bundle).
The raw-graph wire drops the inline build_log_id; the client fetches a
node's captured output on demand. Two handlers resolve node id -> log-row
id (JobQueue::build_log_id_of, now keyed by the wire u64) then delegate to
the existing get_full / raw handlers: /api/build-log/<node_id> serves the
BuildLogFull JSON ({stdout, stderr} + header), /raw serves text/plain.
404 when the node has no linked log.
