Clarify dependency summary counts and query exhaustion

[Widthdom]

Fixes #5346

deps --summary-only --json now identifies count as the returned page count and reports additional-result evidence, candidate coverage, query exhaustion, and total-count availability/authority. A complete reference graph no longer implies a complete dependency query. Ordinary summaries reuse the existing bounded ranking window; cycle summaries reuse existing SCC totals. Workspace summaries explicitly report unverified candidate exhaustion.

Validation:

• Solution build: zero warnings/errors.
• Related dependency, JSON snapshot, and CLI help tests: .NET 8 — 433 passed; .NET 9 — 432 passed, 1 existing skip.
• Limits 1/2/3/4, empty/missing/incomplete graphs, candidate caps, filters, generated/test exclusions, reverse queries, workspace and batch payloads, and response budgets covered.
• Repository and workspace index checks passed. Repository smoke checks at limits 1 and 2 report has_more=true with non-authoritative/unavailable totals.
• Changelog fragment validator passed.
• Mixed-language SQL readiness and filtered-lookahead regressions cover the adversarial review findings.
• Codex adversarial review: two rounds; both initial P2 findings fixed. Final result: No blocking/actionable issues found. The reviewer independently passed both focused regressions on .NET 8 and .NET 9.

Documentation: bilingual count/completeness reference in docs/deps-summary-counts.md, linked from USER_GUIDE.md; updated CLI help and bilingual testing guidance. Changelog: changelog.d/unreleased/5346.fixed.md.