Key extraction

• Literal + template observation: packages/cli/src/core/extractor/keySites/scan.ts emits KeyObservation[] for:
  • literal
  • template_resolved (via const substitution)
  • template_partial (unresolved placeholders kept as structured data)
• Const substitution trace: packages/cli/src/core/constmap/resolve.ts exposes resolveKeyPlaceholdersWithTrace() so extraction can include ordered substitution steps.
• Project orchestration: scanProjectKeyObservations() walks srcRoot, adds span.filePath, and is suitable for CLI/report payloads.
• Dynamic heuristic scan: packages/cli/src/core/extractor/dynamic/ detects non-literal first args and comment-aware sites for diagnostics (validate, locales dynamic).
• Parsing strategy: scanners parse exact translation call spans first, then evaluate only the first argument expression. This prevents preview bleed into neighboring code and supports multiline/comment-heavy calls.
• Multiline signal: observations/sites preserve whether a call is multiline (isMultilineCall) so JSON/report consumers can prioritize complex call sites.
• Validation behavior: validate compares resolved literal/template keys to source locale leaves; dynamic findings are reported separately.