create-issue `deduplicate-by-title` validates but is never emitted to the safe-outputs config (silent no-op)

[norrietaylor]

Summary

safe-outputs.create-issue.deduplicate-by-title passes schema validation and is documented, but the compiler never serializes it into the generated .lock.yml safe-outputs config. The runtime handler (issue_title_dedup.cjs) reads config.deduplicate_by_title, which is therefore always undefined — so configuring the field has no effect. No error, no warning; it silently does nothing.

Repro

wf.md:

---
on: workflow_dispatch
engine: copilot
strict: false
safe-outputs:
  create-issue:
    deduplicate-by-title: 1
    max: 3
---
# t
body

$ gh aw compile wf.md --validate --approve
✓ Compiled 1 workflow(s): 0 error(s), 0 warning(s)

$ grep -oE '"create_issue":\{[^}]*\}' wf.lock.yml
"create_issue":{"max":3}            # <- no deduplicate_by_title

$ grep -ci deduplicate wf.lock.yml
0

Expected

The emitted create_issue safe-outputs config contains deduplicate_by_title (e.g. "deduplicate_by_title":1) so the runtime parseDeduplicateByTitle(config.deduplicate_by_title) path is active.

Actual

deduplicate-by-title is parsed-and-dropped; absent from the lock entirely. Title-based dedup never runs.

Root cause

The compiler config struct in pkg/workflow/create_issue.go has no field for it. The struct binds the sibling options but not this one:

TitlePrefix      string   `yaml:"title-prefix,omitempty"`
Labels           []string `yaml:"labels,omitempty"`
CloseOlderIssues *string  `yaml:"close-older-issues,omitempty"`
CloseOlderKey    string   `yaml:"close-older-key,omitempty"`
GroupByDay       *string  `yaml:"group-by-day,omitempty"`
Expires          int      `yaml:"expires,omitempty"`
Group            *string  `yaml:"group,omitempty"`
// (no `yaml:"deduplicate-by-title"` binding)

Meanwhile the runtime expects it — actions/setup/js/issue_title_dedup.cjs exports parseDeduplicateByTitle(), and create_issue.cjs calls parseDeduplicateByTitle(config.deduplicate_by_title). The frontmatter→config wiring is the missing link.

Versions affected

Validates-but-drops on v0.75.4, v0.76.1, v0.77.5, v0.77.6 (the struct lacks the field in all). v0.74.3 rejects it outright (Unknown property: deduplicate-by-title), so the field appears to have been added to the schema/docs/runtime around v0.75 without the compiler binding.

Impact

Workflows relying on deduplicate-by-title for per-finding issue dedup get duplicate issues with no indication the setting is inert.