[X-Guardian]

Description

Summary

Migrates the cdktn package to the standard src/ (sources) + lib/ (build output) layout used by every other workspace package. Sources and compile output were previously co-located in lib/, which caused stale .js/.d.ts artifacts to confuse knip after every local yarn build (false-positive "unused dependency" reports for json-stable-stringify, yazl, @types/json-stable-stringify, @types/semver because TS module resolution was preferring the stale .d.ts typings over the actual .ts sources).

Why

• After #116 migrated other packages to src/ → build/, cdktn was the only holdout still emitting compiled output next to sources.
• Mixed layout meant knip would silently fail locally after a build, even though it was clean in CI (CI runs knip on a fresh checkout with no compiled artifacts).

What changed

Source layout:

• 85 .ts source files moved: packages/cdktn/lib/**/*.ts → packages/cdktn/src/**/*.ts (subdir layout preserved: backends/, functions/, hcl/, private/, synthesize/, testing/, tokens/, validations/)
• package.json "main" and "types" continue to point at lib/index.js / lib/index.d.ts — distribution surface is unchanged.

Build configuration (packages/cdktn/package.json):

• Added "jsii"."tsc": { "outDir": "lib", "rootDir": "src" } — JSII regenerates tsconfig.json to compile from src/ and emit to lib/.
• Added "jsii"."excludeTypescript": ["src/**/__tests__/**"] — three colocated __tests__ files inside src/testing/ import from test/helper/ (outside rootDir); excluding them keeps JSII's rootDir constraint satisfied. Jest still picks them up via testMatch.

Test wiring:

• 33 test files + 5 helpers updated: from "../lib" → from "../src" (and ../../lib → ../../src for nested test/helper/ and test/tokens/ files).
• Added packages/cdktn/tsconfig.test.json — extends the JSII-generated tsconfig.json but widens rootDir to . and excludes lib/**/*.d.ts. Required because (a) test files live outside rootDir: src and ts-jest can't compute output paths for out-of-tree files, and (b) without excluding lib/, ts-jest sees both src/terraform-count.ts and lib/terraform-count.d.ts as separate type declarations and rejects assignment between them.
• Updated jest.config.js to point ts-jest at tsconfig.test.json.

Knip + docs:

• knip.jsonc — packages/cdktn workspace project glob updated to ["src/**/*.ts", "test/**/*.ts"]; entry list dropped (knip auto-detects src/index.ts).
• CLAUDE.md, CONTRIBUTING.md, tools/generate-function-bindings/README.md — cdktn/lib/... paths in docs updated to cdktn/src/....

Checklist

• I have updated the PR title to match CDKTN's style guide
• I have run the linter on my code locally
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation if applicable
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works if applicable
• New and existing unit tests pass locally with my changes

[github-actions]

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