feat(cli): plumb lint --suggest-ignores

[aram-devdocs]

Summary

Analyze repeated noise and propose ignore rules with selectors
that would silence the top N patterns. Writes the proposed
ignores to stdout as a plumb.toml fragment.

Crate / area

plumb-cli — the plumb binary (only crate allowed stdout/stderr + anyhow)

Phase / batch

Part of #65 → Batch 7D (Codegen + watch + suggest-ignores).

Effort: M

PRD references

• PRD §16

Acceptance criteria

• Proposals deduplicate by (rule, selector pattern).
• Top-N configurable via flag.
• No writes to disk — user applies manually.

Dependencies

• None (first in batch; batch-level deps gate this).

Review gates

• 02-spec-reviewer
• 03-code-quality-reviewer
• 05-architecture-validator
• 04-test-runner

How to deliver

Dispatch /gh-issue <this-issue-number>. See the root AGENTS.md and the scoped plumb-cli/AGENTS.md for the invariants that apply.

Suggested delivery: gh-issue