feat: selector-scoped [[ignore]] runtime suppression

[aram-devdocs]

Summary

• Adds a [[ignore]] array to plumb.toml that silences violations by exact CSS-selector path (and optionally by rule_id). Each entry carries a required reason so reviewers can audit what the config silences.
• Engine adds RunReport { reported, ignored } and run_report/apply_ignores; run/run_many keep their Vec<Violation> signature (filtered output) so library callers see no break.
• Pretty output appends N violation(s) suppressed by config; the JSON envelope grows "ignored": N. SARIF stays unchanged (the 2.1.0 schema has no slot for non-standard counts).
• Closes the loop with --suggest-ignores: the suggestion list maps 1:1 onto [[ignore]] entries, so a user can pipe the suggestions into plumb.toml and converge on a clean dogfood exit.
• Wires docs/plumb.toml into the dogfood workflow with [[ignore]] blocks for the mdBook chrome PRD §15 calls out.

Implementation notes

• IgnoreRule is #[serde(deny_unknown_fields)] — typos in plumb.toml surface as parse errors, not silent drops.
• Selector matching is exact-string equality on Violation::selector, deliberately not a CSS-engine match — keeps the engine free of scraper/cssparser runtime overhead and preserves determinism.
• Config.ignore uses #[serde(default, skip_serializing_if = "Vec::is_empty")] so plumb init-emitted configs don't gain a stray ignore = [] line.
• Selector iteration is over a Vec (declaration order); the partition is short-circuited per violation. Both reported and ignored preserve the engine's pre-sorted Violation::sort_key order — apply_ignores is byte-deterministic across runs.
• Schema regenerated via cargo xtask schema; xtask pre-release is green.

Test plan

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo nextest run --workspace --all-features — 492 tests passed
• just determinism-check — three runs byte-identical
• cargo deny check
• cargo audit
• cargo run -p xtask -- pre-release
• Local end-to-end loop: plumb lint plumb-fake://hello --suggest-ignores --format json → parse → write [[ignore]] → plumb lint --config <file> exits 0 with 1 violation suppressed by config footer.
• CI dogfood job: cargo run -p plumb-cli -- lint --config docs/plumb.toml https://plumb.aramhammoudeh.com/ (could not run locally — the macOS Homebrew Chromium binary's WS handshake fails against the deployed CDP driver). The dogfood worker uses browser-actions/setup-chrome, which is the supported configuration. The seeded [[ignore]] list covers the obvious mdBook chrome; any selector I missed will surface in the dogfood log and a follow-up PR can extend it.

🤖 Generated with Claude Code

[github-actions]

I have everything I need. Here is the structured review.

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PR #227 — feat: selector-scoped [[ignore]] runtime suppression

Crates touched: plumb-core, plumb-format, plumb-cli; schema + examples.

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1. Determinism

apply_ignores iterates a Vec in declaration order and preserves caller-sorted order in both output buckets — deterministic. ✓

serde_json::Map envelope insertion order: the pre-existing comment at crates/plumb-format/src/lib.rs:147 ("inserts keys alphabetically") is accurate. ignored → plumb_version → run_id → stats → [suggested_ignores →] summary → violations is alphabetical, so both BTreeMap (default) and IndexMap (preserve_order) produce identical output. ✓

No SystemTime::now, rand::*, HashMap/HashSet in any observable path. ✓

2. Workspace layering

No new cross-crate deps. plumb-core re-exports remain confined to plumb-core internals. plumb-format only adds functions that take &[Violation] + usize. ✓

No unsafe outside plumb-cdp, no println!/eprintln! in library crates. ✓

3. Error handling

IgnoreRule, RunReport, apply_ignores, run_report are all infallible — appropriate. json_with_ignored / json_with_suggested_ignores_and_ignored return Result<String, serde_json::Error> and document # Errors. ✓

No unwrap/expect in non-#[cfg(test)] library code. let _ = writeln!(out, …) is harmless (String::write_fmt is infallible) but slightly unusual; write!(out, …) followed by no suppression would be cleaner — not a blocker.

4. Test coverage

Golden snapshot, unit tests in engine.rs, config round-trip tests, and 6 integration tests in cli_integration.rs all land. Coverage is solid.

5. Documentation

RunReport, IgnoreRule, apply_ignores, run_report, and all new pretty_*/json_* functions are documented. ✓

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Punch list

crates/plumb-core/tests/golden_ignore_filter.rs:784–789 — factually wrong comment (REQUEST_CHANGES)

The comment says "leaving two reported and two ignored" but the committed snapshot has five reported and three ignored (4 divs × 2 rules = 8 raw; selector-only on nth-child(1) suppresses 2, selector+rule_id on nth-child(2) suppresses 1 more). The comment also mentions only spacing/grid-conformance while spacing/scale-conformance is equally involved. Per the no-legacy-code rule, a comment that is factually wrong about the test's own partition must be corrected before merge.

CHANGELOG.md — missing Unreleased entries (REQUEST_CHANGES)

Three user-visible changes are absent from ## [Unreleased]:

• [[ignore]] array in plumb.toml (new config key).
• Pretty output footer "N violation(s) suppressed by config".
• JSON envelope gains "ignored": N on every run (breaking for strict-schema consumers).

CLAUDE.md: "Update the CHANGELOG under ## [Unreleased] only for user-visible changes." All three qualify.

crates/plumb-core/src/lib.rs:33 — apply_ignores re-exported with an implicit sort precondition (warning)

pub use engine::{RunReport, apply_ignores, run, run_many, run_report};

apply_ignores preserves caller order, which must be sort_key ascending order. A caller who constructs their own Vec<Violation> and passes it unsorted gets silently wrong output. The function doc (in engine.rs) mentions this, but the lib.rs re-export adds no signal. Either drop apply_ignores from the re-export (only run_report + RunReport are needed by consumers) or add a # Preconditions note at the function-level doc. Not a blocker, but the next person to call this from downstream is going to miss it.

schemas/plumb.toml.json — ignore field missing "default": [] (minor warning)

rules carries "default": {}. The ignore array has no "default", so LSP/IDE schema validators may flag it as required. Worth checking whether schemars emits a default from #[serde(default)] on Vec<_> — if not, add it manually or via a #[schemars(default)] attribute.

MCP gap (informational)

plumb-mcp still routes through run_many, so ignored_count is invisible to the MCP lint_url / lint_page_html tools. CLI and MCP now give inconsistent auditability. Not a rule violation, but worth a tracking issue.

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Verdict: REQUEST_CHANGES

[aram-devdocs]

Surgical revert: dropped docs/plumb.toml + dogfood --config wiring

Pushed dce1242 to drop two pieces of this PR while keeping the [[ignore]] feature itself:

Removed:

• docs/plumb.toml — the 50+ entry seeded ignore list for mdBook theme chrome
• .github/workflows/dogfood.yml --config docs/plumb.toml flag (workflow restored to its pre-feat: selector-scoped [[ignore]] runtime suppression #227 state — runs plumb lint https://plumb.aramhammoudeh.com/ with default config)

Kept (unchanged):

• All feature code in crates/plumb-core/{config,engine,lib,report}.rs
• All formatter changes in crates/plumb-format/src/lib.rs
• All CLI threading in crates/plumb-cli/src/commands/lint.rs
• All unit, golden, and integration tests
• The documented [[ignore]] example block in examples/plumb.toml
• schemas/plumb.toml.json regen
• Format snapshot updates

Why

The [[ignore]] feature is the right primitive — it's the eslint-disable equivalent for plumb and end users will need it. But shipping plumb itself with a 50+ entry ignore list against our own dogfood site papers over the real signal: plumb's defaults aren't aligned with the rendered mdBook docs theme. Silencing those warnings via --config docs/plumb.toml lets dogfood "pass" without us actually fixing the underlying mismatch (or revising the PRD §15 acceptance bar).

Follow-up needed

A separate issue should track the honest dogfood fix. Options to consider:

1. Align plumb's default tokens to the actual mdBook theme output.
2. Customize the docs site theme to use plumb's tokens.
3. Revise PRD §15 acceptance to "0 errors" instead of "0 violations" (lets warnings remain visible without failing CI).

Not opening that issue yet — it's a separate decision about which path to take.

Validation

• cargo fmt --all -- --check: clean
• cargo clippy --workspace --all-targets --all-features -- -D warnings: clean
• cargo nextest run --workspace --all-features: 492 passed, 0 failed (1 leaky in plumb-cdp — unrelated)