#2699 serve: use active template instructions for recovery

Description

# Issue: Loop recovery misses instructions from a custom template

Follow up #728. Enabled reasoning-loop recovery searches for a bundled
instruction even when the active template emits a different instruction.

# PR: Resolve recovery instructions from the active template

Resolve executed high/low instructions per Service and replace only the first
system instruction. Preserve generated IDs and bundled fallback.
The existing recovery option remains disabled by default.

Validation: `serve.test_active_template_sentence`; executed branches, computed
instructions, Service isolation, fallback and recovery.