fix(report): distinguish inventories from restyles

[BenSheridanEdwards]

Why does this feature exist?

StyleProof currently labels a newly added node's complete computed-style inventory as hundreds of "computed-style differences." During wrapper or path churn, that makes the report look like a large restyle even when most rows are one-sided head context. Reviewers cannot tell structural churn from matched-path style changes.

What changed?

• Reserve presentation-level computed-style/state-delta counts for paths present on both sides.
• Label added-node values as head-side style inventory — no baseline and render value-only tables.
• Keep raw findings, reviewable certification counts, Action verdicts and CLI exit behavior unchanged.
• Update CLI/report descriptions, README, catching guide, demo report and changelog.
• Add regression coverage for add-only nodes, matched-path restyles, wrapper path churn and forced-state inventories.

Behavioural Proof (with video and screenshots)

Not applicable: this is Markdown/report semantics rather than an interactive UI surface. Generated demo output was regenerated and checked; behavior tests assert the exact report headlines, tables and JSON count separation.

Verification Summary

• Definition of Done: followed .agents/project/DEFINITION_OF_DONE.md.
• Commands run: npm run build; npm run typecheck; npm run lint; npm run format:check; npm run privacy:check; npm test; npm run demo:check; git diff --check.
• Results: 639/639 tests passed; demo report is current; build, type, lint, format and privacy checks passed.
• Gate integrity: raw/reviewable certification tallies and Action/CLI exit behavior remain unchanged; only presentation taxonomy and copy change.
• Known risks or skipped checks: browser E2E was not rerun because capture, screenshots and crop generation are unchanged; release CI will run the browser suite.

Checklist

• Proof above — report behavior is asserted in generated Markdown and JSON regression tests
• If you changed capture/diff/report rendering, ran npm run demo:check; committed demo is current
• npm run build && npm run typecheck && npm run lint && npm run format:check pass
• npm test passes
• Added/updated tests for the change
• Updated documentation and CHANGELOG
• Captured output is unchanged; adopters do not need to regenerate baselines
• Followed .agents/project/DEFINITION_OF_DONE.md
• Visual proof is not applicable because this changes report semantics, not product pixels
• The PR body contains no local paths, private consumer references, or placeholders

[github-actions]

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Coverage, determinism, or report/diff consistency evidence is incomplete — repair the capture or reflow source; visual approval cannot clear this failure.