fix: stabilize integration CI baseline

[hjotha]

Summary

• guard watcher debounce callbacks with a generation counter so stale timers cannot send extra change notifications
• update nanoflow integration fixtures to current MDL syntax
• classify known doctype showcase consistency errors so make test-integration fails only on unexpected validation errors

Validation

make build
go test ./cmd/mxcli/tui -run TestWatcherDebounce -count=20 -v
./bin/mxcli check mdl-examples/doctype-tests/02b-nanoflow-examples.mdl
CGO_ENABLED=0 go test -tags integration -count=1 -timeout 30m ./mdl/executor -run 'TestRoundtripNanoflow_(Loop|EnumParameter|Annotations)|TestMxCheck_DoctypeScripts/02b-nanoflow-examples.mdl|TestMxCheck_DoctypeScripts/03-page-examples.mdl' -v
make test
make lint-go
make test-integration

Closes #411.

[github-actions]

AI Code Review

Critical Issues

• None found.

Moderate Issues

• None found.

Minor Issues

• None found.

What Looks Good

• Watcher debounce fix: The addition of a generation counter (atomic.Uint64) to prevent stale timers from sending extra change notifications is a correct and robust solution for the race condition in the TUI file watcher. The test update appropriately tightens the burst timing to avoid flakiness on slow CI machines.
• Nanoflow example syntax update: The changes to 02b-nanoflow-examples.mdl correct MDL syntax to current standards:
  • Replaced incorrect declare + call returns pattern with direct assignment ($IsValid = call nanoflow ...)
  • Fixed change statement syntax from (IsValid: true) to (IsValid = true) (using = for assignments in procedural statements, consistent with MDL grammar)
  • Removed redundant Admin role from grant execute (minimizing noise while maintaining correctness)
    All changes follow MDL design guidelines: use of qualified names, English-readable statements, proper keyword usage (call, if, change), and diff-friendly edits.
• Test stability improvement: Adding known CE errors (CE0115, CE5601, CE0117, CE6035) to scriptKnownCEErrors ensures make test-integration only fails on unexpected validation errors. This is a prudent approach for stabilizing the CI baseline against known showcase inconsistencies without masking real regressions.

Recommendation

Approve the PR. All changes are well-scoped, technically sound, and directly address the stated goal of stabilizing the integration CI baseline. The modifications follow established patterns in the codebase and maintain full compliance with the project's architectural and style guidelines. No further changes are required.

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[hjotha]

@ako This needs to be merged first and then my PRs should be rebased to fix the CI errors.