docs(#2869): record ADR-2866 install-surface resolution (#3265)

Phase 0 of epic #2866. Records the decision that the install pipeline
resolves surface identity — (runtime × scope × trigger) — as a value
instead of implying it from destination paths.

The ADR makes four things explicit:

- Amends ADR-3660 (placement -> placement + trigger resolution) and says
  why placement-only stopped paying: the /gsd-<name> trigger two
  artifacts collide on is not a value anywhere, so #2218 cannot be
  stated by any module or test.
- Adds one axis to ADR-1016's deliberately-closed descriptor vocabulary
  (host trigger precedence), required-with-default so ADR-894's
  additive-only stability contract holds.
- Records the @-include constraint (expands ~, does NOT expand env
  vars, no conditional syntax) as the reason #2218 triage option 1 is
  REFUTED rather than merely deprioritized.
- Notes the non-conflicts: completes ADR-58 rather than revising it,
  and preserves ADR-1508's dependency direction.

ADR-3660 and ADR-1016 each gain the reciprocal Amended by back-link,
matching the corpus convention ADR-2782 already set on ADR-1016. Each
states that the decision is recorded now while the modules change at
Phase 2 (#2871), so no reader is told a widening has already shipped.

Also corrects CONTEXT.md's Installer Module entry: bin/install.js is
hand-authored, not generated. ADR-1508 states this verbatim and no
build step emits it; the stale annotation invites contributors to look
for a generator that does not exist.

Docs-only. Verified via the remote runner.

Closes #2869

Co-authored-by: sim <sim@local>

docs/adr/3660-runtime-artifact-layout-module.md

@@ -5,6 +5,7 @@
 - **Issue:** #3660
 - **Implementation:** #3663 (Phase 1), feat/3663-runtime-artifact-layout-module-phase-1-m
 - **Subsumed by:** [ADR-1239](1239-gsd-embeddable-orchestration-engine.md) (GSD as an Embeddable Orchestration Engine) — read it first; see the amendment below
+- **Amended by:** [ADR-2866](2866-install-surface-resolution.md) (Install-surface resolution) — **this module widens from *placement* to *placement + trigger resolution*.** The `Layout` returned here models where a file goes but not the `/gsd-<name>` trigger it occupies, so nothing in the tree can express the cross-scope collision in [#2218](https://github.com/open-gsd/gsd-core/issues/2218). ADR-2866 adds a projection returning the resolved trigger, its kind and scope, its destination, and whether another install shadows it. **This ADR's placement decision is unchanged and still in force** — `resolveRuntimeArtifactLayout` stays for callers that only need placement, the per-runtime table remains the single owner of placement knowledge, and legacy-layout migrations stay in [ADR-0008](0008-installer-migration-module.md). **Timing:** the decision is recorded and `Accepted`; the module changes at epic [#2866](https://github.com/open-gsd/gsd-core/issues/2866) Phase 2 ([#2871](https://github.com/open-gsd/gsd-core/issues/2871)), not before — until then this module resolves placement only.
 
 ## Amendment (2026-07-16): subsumed by ADR-1239 (EoS)