The `--open-issue` run proposed 800+ entries, all `rcppparallel-bundled-tbb` on
ubuntu-2604, each pre-filling `RcppParallel/disable-tbb.patch` for an unrelated
package (ACEsimFit, AovBay, ...). Those packages fail only because their
RcppParallel *dependency* does not build there, so bincraft records
RcppParallel's TBB error text against each dependent and they all match the
signature. Applying a RcppParallel source patch to a dependent's source is not
just noise -- it is broken (the diff targets RcppParallel's Makevars.in).
Add an optional `applies_to` field pinning a package-specific fix to the package
it targets. A signature whose fix is a curated per-package source patch
(rcppparallel-bundled-tbb -> RcppParallel) is only ever proposed for that
package; other matching packages are downstream failures reported as "blocked on
<dependency>" and never proposed a bogus entry. Fix the dependency once and the
whole cascade clears.
- gate proposal generation in build_triage_report on applies_to, add blocked_on
- surface blocked groups in the report and proposer instead of a misleading
"already registered" note
- cover both the dependent-blocked and RcppParallel-itself-proposed cases
Implements steps 1 + 2 of #115: turn recorded build failures into triaged patch suggestions instead of hand-scraping Crow logs.
## What this adds
A **read-only** reporting pipeline over the `single_builds` metadata table. It never writes to the DB or the registry.
- `local/failing-builds-classify.R` — pure, DB-free helpers:
- `normalise_error()` strips temp paths, version numbers, hex addresses, and the package name so the same root cause collapses to one fingerprint.
- `fingerprint_error()` extracts the salient error line and normalises it.
- `classify_error()` matches against a seed signature set; unmatched errors are never guessed at.
- `propose_registry_entry()` renders a schema-valid `registry.json` entry.
- `local/failing-builds-report.R` — entrypoint: queries `single_builds WHERE error_occurred = TRUE AND removed = FALSE`, groups by root cause (signature when classified, fingerprint otherwise), classifies each group, and prints a triaged report. Flags: `--platform`, `--arch`, `--min`, `--json`; `PLATFORM`/`ARCH` env fallbacks.
- `local/tests/test-failing-builds-classify.R` — unit tests for the helpers.
- `local/patches/README.md` — documents the workflow.
## Seed signatures
Each rule carries a fix tier, confidence, and an auto/human-only flag:
| Signature | Fix | Disposition |
| --- | --- | --- |
| `tbb/tbb_stddef.h: No such file` | makevars `-DTBB_INTERFACE_NEW` | auto-proposable |
| RcppParallel bundled TBB (musl / new g++) | curated `disable-tbb.patch` | auto-proposable |
| system `libuv.so` link leak | force vendored/static lib | **human triage** (novel source diff) |
| unmatched | none | **human triage** |
## Guardrails honored
- No autonomous novel source diffs: only known env/makevars levers and already-curated package patches are auto-proposable; anything needing a brand-new diff, and any unknown signature, is routed to human triage.
- No DB or registry writes; no change to the public `src/contrib` index.
- Reuses `single_builds.error_text`; no new failure-capture pipeline.
## Verification
- All helper unit tests pass under the Dockerized R 4.5.3 build env.
- Pre-commit hooks pass (`air-format`, `validate-patches`, prettier, etc.).
- Smoke-tested the full report path with a stubbed DB; generated proposals pass the real `local/validate-patches.R`.
Steps 3 (auto-open PRs) and 4 (feedback loop) are intentionally deferred, per the issue's suggestion to validate the signature set first.
Closes#115
Reviewed-on: #116
