feat(ui): share the app bins' boot glue in @deepseek-ai/dsh-app-boot

The four near-twin helpers the two published bins carried — loadEnv,
installFailLoud, assertEntriesLoaded, boot — live once in
packages/ui/app-boot, parameterized by the bin's diagnostic prefix and
injectable at their side-effect seams (warn sink, process slice), so
every branch sits under the per-file 100% coverage gate: the unit suite
drives boot() in-process against the real Loader (relative-specifier
configs) through both the settled-tree path and the fiber-less-entry
rejection, and exercises the ENOENT/unloadable .env split, the
Error/non-Error/stackless fail-loud arms, and the disabled-entry
exclusion. resolveConfigPath (snapshot-aware) becomes the single path
resolver for both bins.

Each bin.ts is now a thin self-executing composition plus its
app-specific lifecycle (acp: replay env-skip + stdin-EOF dispose;
stdio: nothing extra), exports nothing, and stays coverage-excluded;
the built-bin smokes still prove both artifacts under plain node in the
node_modules-shaped temp dir (now symlinking ui/app-boot), including
the missing-config non-zero exit.

Implements docs/rfc/implemented/simplification/2026-07-04-share-app-bin-boot-glue.md
(moved from proposed/ and amended); the extract-example-app-packages
RFC's bin-ownership facts are amended in the same change.

AGENTS.md

@@ -112,6 +112,8 @@ packages/    Harness packages, grouped by role at packages/<group>/<pkg>/.
                     front door)
     acp-agent/      ACP server APP: agent-core spine + JSONL persistence + the
                     acp bridge, NO stdout logger + a bin (the demo:acp front door)
+    app-boot/       shared boot glue for the two app bins: .env loading,
+                    fail-loud Loader guards, config resolution, boot sequence
   support/        dev/test/example infrastructure (lower compat expectations)
     invariants/     dev-mode event-contract invariants + session-log freeze
     llm-replay/     record/replay adapter: short-circuits llm/stream from a