fix(validate): coverage diagnostics name the link + satisfier types (REQ-147, #350)

[avrabe]

Addresses #350 (the actionable, schema-agnostic half).

Problem

Marking a sw-req implemented then running rivet validate produced coverage diagnostics that said what was missing but not how to satisfy it. The reporter authored a verification linking directly to the sw-req, got a link-target rejection, and only then reverse-engineered the required shape — "a whole detour."

Fix (no rule semantics changed)

1. The required-backlink coverage diagnostic now names the incoming link type + allowed source types inline:

   Every SW requirement should be verified … — needs an incoming verifies link from one of [sw-verification, unit-verification, sw-integration-verification]

2. The Lifecycle coverage gaps summary now points at rivet validate --explain <ID>, which lists each rule's satisfied/MISSING state with the exact incoming link + source types (and alternates). Verified the pointer resolves to that breakdown.

Verification

• New aspice repro: a sw-req with no verification backlink now shows the link + types inline; the gaps summary prints the --explain pointer; --explain gives the per-rule breakdown.
• All 74 validate::tests pass; clippy --all-targets + fmt clean; rivet validate + rivet docs check PASS.

Triage of #350's other points

• Suggestion 2 (allow direct test→sw-req, or a scaffold-verification command) is ASPICE/schema intent — maintainer call.
• Suggestion 4 (crate: undeclared-field noise) is already mitigated by rivet validate --min-severity warning (REQ-137) + schema extends.
• Filed REQ-148 (draft): a generic coverage-rule-consistency meta-check — the aspice swe1-has-verification rule advertises from-types (unit-verification, sw-integration-verification) that no link rule permits to verifies→sw-req, which is why the reporter's direct link was rejected. Deferred: needs conservative implementation (target constraints live in both link-types and per-type link-fields) to avoid false positives, and whether the aspice from-types is itself wrong is a compliance-semantics call.

Implements: REQ-147

🤖 Generated with Claude Code

[github-actions]

📐 Rivet artifact delta

Change	Count
Added	2
Removed	0
Modified	0
Downstream impacted (depth ≤ 5)	0

Graph

graph LR
  REQ_147["REQ-147"]:::added
  REQ_148["REQ-148"]:::added
  classDef added fill:#d4edda,stroke:#28a745,color:#155724
  classDef removed fill:#f8d7da,stroke:#dc3545,color:#721c24
  classDef modified fill:#fff3cd,stroke:#ffc107,color:#856404
  classDef overflow fill:#e2e3e5,stroke:#6c757d,color:#495057,stroke-dasharray: 3 3

Loading

Added

• REQ-147
• REQ-148

📎 Full HTML dashboard attached as workflow artifact rivet-delta-pr-394 — download from the workflow run.

_{Posted by rivet-delta workflow. The graph shows only changed artifacts; open the HTML dashboard (above) for full context.}

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rivet-core/src/validate.rs	75.00%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!