[karim-alweheshy]

Summary

• Add an opt-in Xcode configuration for native compilation and linking of
  selected Preview targets, while leaving ordinary configurations Bazel-owned.
• Prepare the selected target's declared Swift, Clang, generated-header, plugin,
  macro, and linker inputs from Bazel so Xcode can compile the Preview source
  with its native toolchain.
• Keep Preview-analyzer path anchoring, static-library argument mode and
  runtime-policy preparation with their native consumers in this change.
• Keep test, archive, and production configurations on the normal Bazel build
  path. Resource-bundle migration/staging is handled by the follow-up resource
  change.

Based on branch preview-stack-compiler-inputs-v2.

The opt-in and its required compiler/link/runtime plumbing stay together so no
intermediate merge exposes an incomplete configuration. The separate linker
and indexing improvements are already in the base. Resource bundles are outside
this chunk; the checked-in example makes that limitation explicit.

Review order

1. Public preview_xcode_configurations option and project/configuration settings:
   check that only named configurations opt in and archive attempts are rejected.
2. Selected-target compiler inputs and native link/runtime preparation:
   check the producer-to-consumer contract, static dependency closure, generated
   headers, test hosts, frameworks, and mixed-language targets.
3. Regression tests and examples/previews: check ordinary configuration
   preservation and the supported scheme/source pairings.

Validation

This resegmented branch has exactly the same Git tree as the previously
CLI-validated candidate. Root tests and lint are rerun at this head. The example
CLI/build/staging evidence below is reused from that identical tree, not claimed
as a new execution during this split.

• All 134 root Bazel 9 test targets plus the generated-docs test pass at the
  proposed head on macOS with Xcode 27.0. Repository Buildifier passes.
• The resource-free example generates with its checked-in rules_swift 3.5 and
  rules_apple 4.4 pins, using this repository through local_path_override.
• Ordinary Bazel builds of the macOS app, framework, and explicit-module target
  pass. An ordinary Xcode Debug build of the macOS app also passes.
• Native Previews-configuration CLI builds pass for the library, mixed-language,
  framework, macOS app, explicit-module, and generic iOS Simulator schemes.
  The final assembled source was regenerated and the mixed/explicit schemes
  rerun. CLI builds used CODE_SIGNING_ALLOWED=NO.
• Shell checks report no new findings; existing template warnings are unchanged
  from main. Generated documentation retains its required trailing blank line.

This is a draft extraction with compile/link/packaging evidence, not fresh Canvas
render or signed-runtime proof. The assembled stack still needs visual retesting.
The separate rules_swift 4.1 fixture is not included: ordinary compilation with
the installed Xcode 27 SDK crashes before a Preview action can run.

Testing

• Generate the example project with the Preview configuration opted in.
• Verify ordinary Debug build/test/archive actions remain Bazel-owned.
• In Xcode, select a Preview scheme configured for native compilation, request
  a Preview, and record the first terminal result. A successful build alone is
  not a successful Preview; confirm the expected view actually renders before
  making that claim.