feat(supplier): Phase 2 — federation handshake + FederationProvenance (#288)

[avrabe]

Closes #288.

Implements Phase 2 of the cross-org / supplier traceability track laid
out in docs/design/cross-org-supplier-traceability.md §6 (Phase 1
shipped in #286 / v0.10.0). The MVP described the boundary; this PR
makes the boundary crossable: structured cross-org link semantics, a
ReqIF backend for cited-source, a rivet supplier pull command,
and the cross-org provenance block that imports stamp.

Phase 2 scope coverage

1. derives-from-external link type with structured target — DONE

• New Link.external: Option<ExternalLinkTarget> field. When YAML
  target: is a mapping (the cross-org *-external link types),
  Link.target mirrors the mapping's anchor: for graph navigation
  and the full {org, contract, doc-id, last-synced, sha256, anchor}
  payload flows into Link.external. Flat-string targets round-trip
  unchanged via a custom serde impl.
• derives-from-external link type added in schemas/common.yaml
  with inverse derived-into-external.
• yaml_hir.rs CST link extractor handles the structured shape by
  dedenting the value text and round-tripping through serde_yaml.
  Regression-guarded against the previous "silently mis-target at the
  first mapping key" behaviour.

Tests: model::tests::link_flat_target_yaml_roundtrip,
link_structured_target_yaml_parse,
link_structured_target_yaml_serialize_then_parse,
link_structured_target_requires_anchor,
yaml_hir::tests::links_extraction_structured_external_target.

2. cited-source: kind: reqif backend — DONE

• CitedSourceKind::is_local_phase2() admits Reqif alongside File.
• resolve_reqif_uri() handles reqif://, file://, and bare-path
  forms (HTTP(S) ReqIF endpoints remain Phase 3+).
• check_cited_source for kind: reqif: read bytes, sha256, verify
  stamp → Match / Drift / MissingHash. Adds a ReqIF XML
  well-formedness check via reqif::parse_reqif so a malformed
  supplier delivery surfaces as FileError at validate time rather
  than poisoning the cache later.

Tests: cited_source::tests::check_cited_source_reqif_* (4 tests +
resolve_reqif_uri_handles_scheme_and_relative).

3. rivet supplier pull <anchor> for kind: file | reqif — DONE

• New CLI subcommand: rivet supplier pull <anchor> [--format text|json]. Looks up the anchor by ID, validates type, parses
  cited-source, fetches local payload, cross-checks the stamped
  sha256 against wire bytes. Refuses to write a poisoned cache entry
  on drift (auditor must re-stamp).
• For ReqIF, also runs parse_reqif before caching to gate malformed
  XML.
• Writes payload + sibling <anchor>.manifest.yaml under
  .rivet/supplier-cache/<org>/<contract>/ (path components
  sanitised to alphanum + -_. so a contract typo can't escape the
  cache root).
• Idempotent: a re-pull with identical bytes refreshes only the
  manifest's fetched-at; the JSON output reports
  bytes_unchanged: true.

Tests: cli_commands::supplier_pull_kind_file_writes_cache_and_manifest,
supplier_pull_refuses_on_sha256_drift,
supplier_pull_idempotent_on_re_run,
supplier_pull_kind_reqif_writes_reqif_extension,
supplier_pull_unknown_anchor_errors.

4. FederationProvenance block on imported artifacts — DONE

• New FederationProvenance struct: {source-org, source-tool, source-id, anchor, fetched-at, source-hash, mapping-recipe}.
  Wired into Provenance as an optional federation: field — None
  for first-party / AI / human artifacts; serialises out only when
  present (backward-compatible with existing AI-provenance YAML).
• rivet supplier pull stamps the block into the cache manifest. The
  same shape is what Phase 3 mapping-recipe imports will write onto
  the imported artifacts themselves.

Tests: model::tests::federation_provenance_yaml_roundtrip,
provenance_federation_block_is_optional. The end-to-end
supplier_pull_kind_file_writes_cache_and_manifest asserts the
emitted manifest carries source-org, source-tool, anchor, and
source-hash.

Deferred to follow-up

Per the design doc §6 Phase 3 scope (explicitly out of scope here):

• Field-mapping recipes under schemas/supplier-mappings/.
• rivet supplier publish (rivet-to-rivet manifest emission).
• OSLC / Polarion / GitHub-issues backends for cited-source.
• Variant-aware anchors (when: clause on external-anchor).
• rivet supplier promote <anchor> for converting delegated chains
  to first-party.

Commit layout

Three logical commits, all carrying mandatory traceability trailers:

1. feat(supplier): derives-from-external structured target + FederationProvenance (#288) — Implements: REQ-010 / Refs:
   REQ-020, FEAT-001.
2. feat(cited-source): kind: reqif backend with sha + XML well-formedness gate (#288) — Fixes: REQ-004.
3. feat(supplier): rivet supplier pull <anchor> — federation handshake (#288) — Implements: REQ-007.

Test plan

• cargo fmt --all
• cargo clippy --workspace --all-targets -- -D warnings
• cargo build --workspace
• cargo test --workspace — 1006 lib tests + every integration
  test passes; the 6 new model unit tests, 4 new cited-source
  reqif tests, 1 new yaml_hir CST test, and 5 new supplier-pull
  integration tests all pass; oracle-gated (each fails without the
  corresponding change).
• rivet validate — same baseline result as main (6
  pre-existing errors in the spar-external project unrelated to this
  PR; reproduced cleanly on a git stash of these changes).

https://claude.ai/code/session_01Ms4nZDTtdfzvzTu8m3ghSj

---

Generated by Claude Code

[github-actions]

📐 Rivet artifact delta

No artifact changes in this PR. Code-only changes (renderer, CLI wiring, tests) don't touch the artifact graph.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Rivet Criterion Benchmarks'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 514b57a	Previous: 284b51c	Ratio
store_insert/10000	16257587 ns/iter (± 587105)	12624029 ns/iter (± 339805)	1.29
link_graph_build/10000	31648069 ns/iter (± 1900109)	26094482 ns/iter (± 963800)	1.21
validate/10000	17416126 ns/iter (± 589201)	12995506 ns/iter (± 350432)	1.34
traceability_matrix/1000	67388 ns/iter (± 292)	45966 ns/iter (± 1418)	1.47
query/10000	115461 ns/iter (± 728)	90580 ns/iter (± 1181)	1.27

This comment was automatically generated by workflow using github-action-benchmark.

[codecov]

Codecov Report

❌ Patch coverage is 98.33333% with 7 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rivet-core/src/cited_source.rs	96.12%	5 Missing ⚠️
rivet-core/src/diff.rs	50.00%	1 Missing ⚠️
rivet-core/src/yaml_hir.rs	98.83%	1 Missing ⚠️

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