Update nightly docs reconciler prompt for split config package layout

[Copilot]

The nightly documentation reconciler prompt still pointed at internal/config/config.go and internal/config/validation.go, which no longer reflect the current internal/config/ layout. This caused the workflow guidance itself to reference nonexistent or incomplete sources when reconciling docs against implementation.

• What changed

  • Updated .github/agentics/nightly-docs-reconciler.md to point config-structure checks at:
    • internal/config/config_core.go
    • internal/config/config_stdin.go
  • Updated validation guidance to reference the current validation split:
    • internal/config/validation_server.go
    • internal/config/validation_gateway.go
    • internal/config/validation_rules.go
  • Updated variable-expansion guidance to reference internal/config/expand.go.

• Why this matters

  • Keeps the reconciler’s source-of-truth references aligned with the implementation it is auditing.
  • Reduces false findings and incomplete analysis in future nightly documentation reconciliation runs.

• Prompt update example

  - Verify the configuration JSON structure matches the actual config schema in
    `internal/config/config_core.go` and `internal/config/config_stdin.go`
  
  - Check that constraints (required/optional) match the validation logic in
    `internal/config/validation_server.go`,
    `internal/config/validation_gateway.go`, and
    `internal/config/validation_rules.go`