fix(#2297): scope resolve_model_ids:"omit" to the resolving runtime (#2332)

* fix(#2297): scope resolve_model_ids:"omit" to the resolving runtime

The installer writes resolve_model_ids:"omit" for non-alias runtimes into the
machine-wide ~/.gsd/defaults.json (#1156); any runtime read it back, so install
order silently flipped Claude's adaptive tier aliases (executor->sonnet,
planner->opus) to '' in no-project sessions.

Resolution is now scoped to the runtime actually resolving, identified by a new
per-install <install>/gsd-core/.gsd-runtime marker (installer writes it beside
VERSION). The "omit" branch returns '' only when the PROJECT explicitly set omit
(honored for all runtimes, #2517 finding #4) OR the active runtime lacks native
aliases. Claude ignores a global-defaults-only omit and keeps its aliases; the
active runtime is canonicalized (GSD_RUNTIME -> config.runtime -> marker ->
claude) so alias/case spellings can't defeat the check; explicit project
omit is workstream/project-scope aware; explicit true still materializes IDs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(#2297): backfill PR number 2332 into changeset

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/fixtures/install-tree/augment.json

@@ -106,6 +106,7 @@
   "commands/gsd-verify-work.md",
   "commands/gsd-workspace.md",
   "commands/gsd-workstreams.md",
+  "gsd-core/.gsd-runtime",
   "gsd-core/VERSION",
   "gsd-core/bin/check-latest-version.cjs",
   "gsd-core/bin/ensure-runtime-build.cjs",