Harden standalone bundle generation for @wanman/cli

[Cangminghai]

Changes

• extract standalone bundle generation into a dedicated helper with explicit embedded-asset validation
• prebuild runtime, host-sdk, and cli dependencies before generating the standalone bundle
• add a standalone smoke verifier that runs pnpm --filter @wanman/cli standalone, checks packages/cli/dist/wanman.mjs, and verifies temp asset cleanup
• add focused standalone helper tests for missing assets, invalid manifests, output naming, cleanup, and compile-target branches

Test Coverage

Changed file packages/cli/src/standalone-build.ts coverage:

• Lines: 95.52% (128/134)
• Statements: 93.05% (134/144)
• Branches: 81.63% (80/98)
• Functions: 85.71% (18/21)

Verification

• pnpm --filter @wanman/host-sdk build
• pnpm --filter @wanman/runtime build
• pnpm --filter @wanman/cli typecheck
• pnpm --filter @wanman/cli build
• pnpm exec vitest run packages/cli/src/standalone-build.test.ts
• pnpm exec vitest run packages/cli/src/standalone-build.test.ts --coverage --coverage.reporter=text-summary --coverage.reporter=json-summary --coverage.include=packages/cli/src/standalone-build.ts
• pnpm --filter @wanman/cli test:standalone

Notes

• pnpm --filter @wanman/cli test:unit still hits unrelated pre-existing Windows baseline failures elsewhere in the CLI package, so verification here is targeted to the standalone bundle surface.

[Cangminghai]

Coverage gate not met for changed file \packages/cli/src/standalone-build.ts, so this PR is not merge-ready yet.\n\nCurrent coverage from the PR and local rerun:\n- Lines: 95.52%\n- Statements: 93.05%\n- Branches: 81.63%\n- Functions: 85.71%\n\nTargeted local verification did pass:\n- pnpm --filter @wanman/cli typecheck\n- pnpm exec vitest run packages/cli/src/standalone-build.test.ts\n- pnpm exec vitest run packages/cli/src/standalone-build.test.ts --coverage ...\n- pnpm --filter @wanman/cli test:standalone\n\nPlease add meaningful tests for the remaining untested standalone-build branches until the changed-file coverage clears >=95%, then re-request review.