core: RootEntry type missing default_runtime field (schema/type drift)

[tadasant]

Surfaced during fresh-eyes review of #142.

schemas/roots.schema.json defines default_runtime (added in #146), and packages/core/tests/validator.test.ts covers it, but the RootEntry TypeScript interface in packages/core/src/types.ts was never updated to include default_runtime?: string.

Impact: TS consumers can't read root.default_runtime even though the schema accepts and validates it. Schema/type drift.

Fix: add default_runtime?: string; to interface RootEntry in packages/core/src/types.ts.

Pre-existing on main (from #146), unrelated to the Cursor adapter — filed separately rather than bundled into #142.

[tadasant]

🚦 Issue gate

Kind: bug (⚪ normal) · Scope: convergent · Facets: none

Verdict: AUTO-PROCEED — convergent, no hold test fired. schemas/roots.schema.json accepts default_runtime (#146) and the validator tests cover it, but interface RootEntry never gained the field — schema/type drift, and closing it removes a defect rather than adding capability. Note the direction: adding an optional property to a type so it matches an already-published schema is a widening, which the surface's schema exclusion explicitly does not cover (only narrowing is excluded).

Live pages: none — not alert-shaped, and nothing in pulsemcp/air is deployed (the surface doc: "nothing here is deployed, so nothing pages"), so anchor 2a has no rule to resolve; anchor 2b — quick_search_sessions for pulsemcp/air issue sessions with show_archived: true — returns no alert-genesis session. Normal dispatch.

Rating detail

Axis	Rating	Why
Requirement complexity	medium	The surface doc's own worked example of medium: "a type that drifted from its schema (#147)". The ask itself is one line; understanding which of schema/type/resolver is authoritative is the medium part.
Requirement impact	medium	One field, readable by TS consumers of RootEntry. Not resolveArtifacts and not the composition rules.
Solution complexity	small (est.)	Guessing: default_runtime?: string; on one interface, possibly with a doc comment matching the neighbours.
Implementation risk	small (est.)	Guessing: additive optional field; tsc and the test matrix catch any error immediately.
Estimated cost	small (est.)	Guessing: one file, one line, plus whatever type assertion the tests want.

Note: the three solution-side axes are estimates — there is no diff yet.

Staleness check: live. packages/core/src/types.ts on main contains no occurrence of default_runtime at all; interface RootEntry (line 182) still ends its authored fields at default_in_roots. #150 (docs) and #142 (Cursor adapter) both merged without touching it. No open issue duplicates it.

[tadasant]

Queued on the work backlog at precedence 5950 (small band, position 6 of 8 at the time of writing).
The backlog groomer pulls from the top of that queue — on its 04:00 run, or sooner if the fleet runs out
of work first. A human can pin or re-place this in Zimmer's Issues view.

[tadasant]

Pulled from the work backlog and started: https://zimmer.tadasant.com/sessions/15294 — a spot implementing session. Started by the fleet-maintenance backlog pull (session https://zimmer.tadasant.com/sessions/15284), 2026-09-06.