[Schema] Add packet-level workParallels field (separate from PhaseView.parallels)

[anantham]

Context

Per phase-a curation log §10.2 (docs/sutta-studio/curation/phase-a.md). Surfaced 2026-05-11.

SuttaCentral suttaplex returns work-level parallels for a sutta (e.g., 16 parallels for MN10: DN22, MN119, MA98, etc.). Per phase-a gate decision (c), these don't belong on PhaseView.parallels because they apply to the whole work, not a specific phase. They currently have no schema home.

Proposed shape

type DeepLoomPacket = {
  // existing fields...
  workParallels?: ParallelRef[];          // work-level (suttaplex)
};

Or via TextGraphRefs:

type DeepLoomPacket = {
  textGraphRefs?: { workParallelIds?: string[]; };
};

Affected code

• types/suttaStudio.ts — DeepLoomPacket type
• services/providers/scSuttaplex.ts — provider already emits ParallelRef[], just needs a schema home
• Renderer: About-this-text panel could surface workParallels as a "parallels across the canon" section

Acceptance

• Schema field added (additive, non-breaking)
• One MN10 phase log's evidence bundle wires it through end-to-end
• Renderer change is a separate follow-up issue

Hit count

1/4 phases (phase-a flagged it; phases b/c/d inherited the same gap)