Subcomponents that exist in Figma are not captured in the parent spec, so they read as external

[nathanacurtis]

Found while analysing the render round-trip corpus in specs-testing (workspace workspaces/eg, a 69-component the component library).

Symptom

Some components that exist in Figma as their own COMPONENT_SET are never captured as subcomponents in the owning component's spec. They then surface as instanceOf references that match nothing, so specs analyze dependencies flags them external: true and the render path skips them (see #276 for the skip behaviour itself).

Concrete case in workspaces/eg:

• workspaces/eg/specs/WebHeaderExperimental/examples.yaml references instanceOf: WebHeaderAction
• The Figma file contains a real COMPONENT_SET named Web Header / Action
• WebHeaderExperimental/api.yaml has no subcomponents entry for it
• Result: WebHeaderAction is reported as an external node with no spec, when the component is in fact part of the analysed library

Why this looks like a matching gap

The workspace config (workspaces/eg/specs.config.yaml) sets:

processing:
  subcomponents:
    match:
      - "{C} / {S}"
      - "{C} / _ / {S}"
    exclude:
      - "{C} / Examples / {S}"

Web Header / Action should match "{C} / {S}" against parent title Web Header (Experimental). It does not — most likely because the parent's Figma title carries the (Experimental) suffix and trailing whitespace ('Web Header (Experimental) '), so {C} never matches. That is a hypothesis, not a verified cause; the first task is to confirm it.

Why it matters

• The dependency graph overstates how much of the library leaves the analysed set. _analysis/dependencies.graph.yaml reports 28 externals; 16 of those are subcomponents that resolve fine once matched by their formatted title, and this class accounts for part of the remainder.
• Anything keyed off "is this component in the workspace" inherits the error — instance manifest construction, blast-radius reports, and render dependency resolution.

Scope

In the current corpus this is a small class. After matching every external against subcomponent titles, the genuinely unresolvable residue is:

• 6 asset marks / brand logo (AssetMark*, BrandLogo) — genuinely a different library, correctly external
• 1 glyph (IconGlyph) — a type: glyph element misclassified as an instance edge, tracked separately
• WebHeaderAction — this issue
• ButtonEndVisual plus the flattened variant-member names — a different root cause, tracked separately

So this issue is specifically about subcomponents that exist in Figma but never make it into the parent spec's subcomponents block.

Where to look

• packages/specs-from-figma/src/ — subcomponent detection and the {C} / {S} pattern matching
• workspaces/eg/specs.config.yaml in specs-testing — the config that exercises it
• workspaces/eg/specs/_analysis/dependencies.graph.yaml — regenerate with specs analyze dependencies; this file goes stale and a stale copy will give wrong answers

Verification

• Web Header / Action appears as a subcomponents entry on WebHeaderExperimental
• It no longer appears as an external node in dependencies.graph.yaml
• Audit the other components for the same pattern — a title suffix or trailing whitespace defeating {C} is unlikely to be unique to Web Header

Part of #281.