CI spec persistence (`.talkops/intent.yaml`)

[structbinary]

Currently, the CISpec is generated fresh each time and only lives in the agent's state during a session. This issue is about persisting it to the repository so it can be used for iterative updates.

Why this matters

• Allows CI-Copilot to incrementally update pipelines instead of regenerating from scratch
• Acts as a source of truth for what the CI pipeline should do, separate from the rendered YAML
• Enables diffing: what changed in intent vs. what changed in the rendered output

Proposed behavior

• After generating a CISpec, write it to .talkops/intent.yaml in the repo
• On subsequent runs, load the existing spec and merge/update rather than starting from zero
• Include metadata: last generation timestamp, CI-Copilot version, target platform