fix: constrain *-design to design-level artifacts, no code

[jeromevdl]

Summary

Adds a ## Constraints section to infrastructure-design.md, functionnal-design.md and nfr-design.md stage files, explicitly stating that implementation-ready code belongs in code-generation, not in design stages.

Design artifacts should describe what infrastructure/patterns are needed and why — not ship complete CDK constructs, Lambda handlers, or IAM policy documents. Code snippets are limited to short illustrative pseudocode (≤15 lines) that clarify a design decision.

Fixes #396

Changes

• core/aidlc-common/stages/construction/infrastructure-design.md — added Constraints section
• core/aidlc-common/stages/construction/functional-design.md — added Constraints section
• core/aidlc-common/stages/construction/nfr-design.md — added Constraints section
• dist/ regenerated via bun scripts/package.ts

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[apackeer]

Thanks for the fix, this is a clean and well-placed prose change and it lines up with the intent of #396. Approving in principle, with a short punch list to land it on top of current v2.

Substantive

1. The Constraints paragraph reads well and sits in the right place (right after the MANDATORY line, before ## Steps). The 15-line pseudocode carve-out is a sensible allowance and does not fight the existing stage text.
2. Scope symmetry worth considering (optional, can be a follow-up): core/aidlc-common/stages/inception/application-design.md produces components.md, component-methods.md, services.md, and component-dependency.md, which have the same "code sneaks in" failure mode. Not a blocker for #396 as filed.

Mechanical must-fix before merge

1. Version trio. core/tools/aidlc-version.ts is still "2.0.2" on the branch; v2 is at 2.2.0. Every user-visible PR bumps aidlc-version.ts, adds a matching ## [N.N.N] - YYYY-MM-DD heading + summary to CHANGELOG.md, and updates the README badge. tests/unit/t68-version-changelog-sync.test.ts enforces all three agree. Patches 2.2.1 through 2.2.13 are currently claimed by other open PRs, so at merge time this needs 2.2.14 or later depending on merge order (re-bump on rebase if collision).
2. Regenerate dist/. You did regenerate dist at the branch base, which was correct, but v2 has moved through 2.1.0, 2.1.6, 2.1.7, 2.1.8, and 2.2.0 since then. After the rebase, run bun scripts/package.ts and commit the resulting drift across all four harness trees. bun scripts/package.ts --check is the CI gate and will fail without this.
3. Once rebased, please confirm bun scripts/package.ts --check and the repo typecheck are clean locally.

Small housekeeping

• The PR body spells the file functionnal-design.md; the actual filename is functional-design.md. In-repo everything is correct, just the description.

Rebase notes

Merge-base with v2 is f3ce1b8. The intervening changes to the three files (2.1.7 fde1e1a, which added the "if exists" input-fallback prose, and 2.1.0 e713c4f, which rerouted the record paths) touch different sections than your Constraints paragraph, so git merge-tree reports a clean auto-merge on all 15 files. Straight git rebase origin/v2 should resolve without hand-editing; the only real work is the regenerated dist and the version trio.

Cross-PR heads-up: your PR #404 also modifies nfr-design.md and infrastructure-design.md. Whichever of #402 and #404 lands second will need a small rebase and another bun scripts/package.ts pass, but they do not conflict textually today.

Happy to re-review as soon as the rebased branch is up.