feat(bash): resolve executor config through the bash settings namespace

The capability's namespace is owned by the seam because it names the
capability, not an implementation: a host composes exactly one provider of
ctx.bash, so both executor families register the same namespace with their
own schema and composition entry without ever colliding, and a settings
document carried between platforms keeps resolving on both.

Both executors read their config through a source thunk, so a stored change
reaches the next command. The constructor checks the schema cannot express
become the section validator, refusing a bad value at the write instead of
at the next command. pwsh re-resolves its executable only when the declared
path changed, so an unrelated settings change never re-probes the filesystem.

packages/bash/bash/tsconfig.json

@@ -20,6 +20,9 @@
     {
       "path": "../../sandbox/sandbox"
     },
+    {
+      "path": "../../settings/settings"
+    },
     {
       "path": "../../support/invariants"
     }