Split RepoPrompt into thin executable and app target

[provencher]

Summary

• keep the shipped RepoPrompt product, executable target, emitted binary, bundle, packaging paths, and native product scheme identities unchanged
• make Sources/RepoPromptExecutable a one-file @main shell that delegates to a new internal RepoPromptApp library target owning the existing app implementation
• move root app tests and Objective-C bridging-header ownership to RepoPromptApp while leaving the separate RepoPromptMCP executable dependency intact
• update source-layout guardrails, generated-Xcode manifest contracts, style inputs, and architecture documentation for the split

RepoPromptApp remains an internal SwiftPM target; it is not exposed as a new library product or convenience scheme.

Validation

Passing validation completed for this implementation:

• make dev-lint
• make guardrails
• make dev-swift-build PRODUCT=RepoPrompt
• make dev-swift-build PRODUCT=repoprompt-mcp
• coordinated debug packaging/build
• make xcode-generator-test
• make xcode-validate
• focused regression checks and repeated focused reruns for the affected Agent, Codemap, and DurableArtifact suites
• commit preflight: whitespace, staged-index secret scan, and guardrails passed
• push preflight: clean tree, outgoing-range review, outgoing-range secret scan, and guardrails passed

The required post-commit pr-ready invocation passed its safety phase and coordinated Swift lint. Its full-root lane completed with the order-sensitive failures described below, so the script stopped before repeating the already-passing product-build and generated-Xcode lanes.

Full-root test disclosure

Two earlier full-root runs completed but hit unrelated order-sensitive failures in untouched suites. Prompt failures reproduced on clean main; Agent, Codemap, and DurableArtifact failures passed repeated focused reruns in the implementation checkout.

The post-commit pr-ready run added a third full-root attempt and likewise completed with Prompt preassembly timeouts plus a Codemap/MCP code-structure assertion. This target split changes test imports/module ownership but does not modify those behaviors.

[baron]

Approved from my review.

I checked the target split from RepoPrompt into a thin executable target plus the internal RepoPromptApp implementation target, including the related Package.swift changes, app entry-point seam, Xcode workspace generator updates, source-layout guardrails, style/lint coverage, docs, and the broad test import retargeting.

This looks mechanically complete and well-guarded:

• the RepoPrompt product/binary identity remains intact;
• the implementation target keeps the existing app dependencies/settings/bridging-header ownership;
• tests now target RepoPromptApp instead of the executable wrapper;
• generator and layout guardrails were updated to prevent regression.

I also updated the branch against latest main and fixed the release tooling assertions that still referenced the old Package.swift variable names. A second-opinion review with Claude Fable 5 High found no blocking issues.

Validation now looks good on the updated head: local commit/push preflights passed, make xcode-generator-test passed, make release-selftest passed after the test fix, and hosted CI/Xcode workspace validation are green for the current head.

No blocking findings from me.