* feat(#3626): make CONTEXT.md seam claims checkable via SEAM.*.enforced-by gate
Adds SEAM.<id>.owns / SEAM.<id>.enforced-by=lint-rule:<name>|test:<path>
predicates to CONTEXT.md, generalizing the existing WORKTREE.SEAM.* shape,
plus scripts/lint-seam-enforcement.cjs (wired into lint:ci) which fails
when a declared single-owner seam names no existing, registered
enforcement mechanism. Backs all six current module-level single-seam/
single-canonical-owner claims found in CONTEXT.md, including the Shell
Command Projection Module's Windows-binary-resolution claim via #3619's
local/no-private-binary-resolution rule.
Scope is resolves-only per maintainer decision: the gate proves an
enforcement pointer exists and is registered, not that its surface
covers every file the seam claims. See docs/adr/3626-context-md-seam-claim-gate.md.
Closes#3626
* fix(#3626): back the Package Identity Module's seam claim too
Isolated adversarial review caught a miss in the "no grandfather list"
sweep: the Package Identity Module also declares itself "Single seam
owning GSD's published-package coordinates" and already names its real
enforcement (scripts/lint-package-identity-drift.cjs). Backs it with
SEAM.package-identity.owns/enforced-by=test:tests/package-identity.test.cjs,
bringing the total to 7 backed seams. Also makes explicit, in the design
doc and ADR, that function-level "single owner" sentences inside
already-covered modules (STATE.md Document Module, etc.) are deliberately
out of scope — a seam claim is about a module's boundary, not every
function inside it.
* docs(#3626): backfill changeset PR number
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Co-authored-by: sim <sim@local>