bug: pnpm clean can delete an authored .wesley manifest

[flyingrobots]

Problem

The native manifest discovery path accepts .wesley/config.json, but scripts/clean.mjs recursively removes .wesley. Running pnpm clean can therefore delete a supported authored project manifest, especially when the file is untracked or ignored.

Evidence

• crates/wesley-cli/src/main.rs: discover_manifest_path includes .wesley/config.json.
• scripts/clean.mjs: the exact cleanup directory list includes .wesley and removes it recursively with force.
• docs/topics/artifacts-and-cache.md: slice docs(5/10): consolidate extension and target contracts #747 now discloses the hazard and protects the cross-source fact with an xtask regression.

Acceptance

• pnpm clean preserves an authored .wesley/config.json, or fails closed with an actionable diagnostic before deletion.
• A deterministic regression covers both the manifest candidate and cleanup behavior.
• Artifact and manifest topics describe the resolved behavior.
• pnpm run preflight passes.

Refs #747.

[coderabbitai]

🔗 Related PRs

#497 - chore(release): v0.0.1 [merged]
#529 - Retire leaf legacy packages [merged]
#655 - chore(release): prepare v0.2.0 [merged]
#657 - docs(release): adapt lifecycle runbook [merged]
#734 - chore(release): prepare v0.3.0-alpha.1 (first 0.3.0-line pre-release) [merged]

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