fix: add [next-stage-name] substitution guidance for construction app…

[dferguson992]

…roval messages (#406)

Summary

During the Construction phase, the approval messages after Functional Design, NFR Requirements, and NFR Design always display "Continue to Code Generation" regardless of which stage just completed. The [next-stage-name] placeholder in the completion message template has no guidance telling the AI model what to substitute, so it defaults to the most prominent terminal stage.

Three construction stage files use [next-stage-name] as a placeholder in their Step 7 completion message, but provide no instruction on how to resolve it. Meanwhile, infrastructure-design.md already hardcodes "Code Generation" (correctly, since it's always the next stage after infrastructure design). The other files lack equivalent guidance, causing the AI to guess incorrectly.

Changes

Added a [next-stage-name] substitution instruction block to each affected file, specifying the Construction phase stage ordering and directing the AI to check aidlc-docs/aidlc-state.md for which stages are enabled:

File	Substitution priority
functional-design.md	NFR Requirements → NFR Design → Infrastructure Design → Code Generation
nfr-requirements.md	NFR Design → Infrastructure Design → Code Generation
nfr-design.md	Infrastructure Design → Code Generation

This preserves the adaptive/conditional nature of the workflow (stages can be skipped) while eliminating ambiguity.

User experience

Checklist

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• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Test Plan

Tested in Kiro IDE 1.0.0 (macOS) with a complex multi-unit project request. Verified all four approval gates now display the correct next stage:

After completing	Displayed next stage	✅
Functional Design	NFR Requirements	Correct
NFR Requirements	NFR Design	Correct
NFR Design	Infrastructure Design	Correct
Infrastructure Design	Code Generation	Correct (unchanged)

Previously, all three intermediate stages incorrectly displayed "Code Generation" as reported in #406.

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

[dferguson992]

@awslabs/aidlc-admins

PR is ready to go, idk what is causing the gitleaks failure. I can't reproduce locally with Kiro.

[dferguson992]

@awslabs/aidlc-admins

Just flagging this up.