Open Loop: modes (Autopilot / Technical) via conditions frontmatter

[suleimansh]

Part of #204 (first slice).

Implement the two modes as conditions frontmatter on sibling .md files, no real param engine yet:

loop.md
loop.autopilot.md    # conditions: autopilot  -> overrides loop.md
prompt.md
prompt.technical.md  # conditions: technical  -> overrides prompt.md

UI surfaces two checkboxes: [ ] Autopilot [ ] Technical Control. Revisit real prompt composition only if the sibling files get too duplicative.

[suleimansh]

Follow-up tracked in #245: if the sibling .md files come out too duplicative, that is where we do real parameterized/composable prompts. Frontmatter fan-out first (this issue), #245 only if the duplication proves it out.