docs: add link to FIX_EXPLAIN.md (deep review) into fix/tag-fix-attempt-2

[pyramation]

docs: add link to FIX_EXPLAIN.md (deep review) into fix/tag-fix-attempt-2

Summary

This PR adds comprehensive documentation explaining the tag resolution bug fix implemented in PRs #218 and #219. It includes two main documentation files:

• FIX_EXPLAIN.md: A detailed technical review explaining the original bug (tag leakage in LaunchQLMigrate.deploy), why the CLI test was failing, and how the combined fix addresses the issue
• ATTEMPT2.md: Documents the approach and rationale for the "attempt 2" fix strategy, emphasizing single-source dependency resolution
• README.md: Adds a reference link to the comprehensive explanation

The documentation covers:

• Root cause analysis of empty dependency arrays causing fallback to raw plan dependencies with unresolved tags
• Why lql deploy --no-usePlan was triggering the bug path
• How the fix changes the condition from (resolvedFromDeps && resolvedFromDeps.length > 0) to (resolvedFromDeps !== undefined)
• Dependency qualification and deduplication logic
• Test alignment with fixture semantics

Review & Testing Checklist for Human

• Verify the technical explanations in FIX_EXPLAIN.md accurately describe the actual code changes in the core migration client
• Check that referenced line numbers and code snippets match the current codebase
• Ensure the documentation clearly explains the bug and fix for future developers who encounter similar issues

Notes

This is a documentation-only PR requested by Dan Lynch (@pyramation) to capture the deep technical analysis of the tag resolution fix. The explanation was generated from reviewing the actual code changes, test failures, and commit history across both PRs.

Link to Devin run: https://app.devin.ai/sessions/8b567dc2cd004b25955b0223a775f06d
Requested by: Dan Lynch (@pyramation)

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