Loki Mode

Added

• Zero-config killer first run (R7 of the competitive arc): loki start "<one line brief>" now works and produces a fast, visible artifact, lowering
  time-to-first-value so a new user gets a good first experience instead of a
  blank or heavy one. Built additively, reusing the existing start/quick/proof
  flow (no parallel second start path).

Fixed

• loki start "build a todo app" previously errored "PRD file not found": a
  whitespace one-line brief was misrouted as a PRD file path. detect_arg_type
  now returns a brief type for whitespace args that match no file/issue/path
  pattern; single-token args, .md/.yaml PRDs, issue refs, and empty input
  all behave exactly as before (back-compat preserved).

Notes

• The brief path applies a genuinely lighter profile (capped iterations, council
  off, simple tier, heavy phases off) for a fast first pass, then emits an R1
  proof-of-run as the visible artifact and prints honest "what next / go deeper"
  guidance (full-depth loki start or loki start ./prd.md). The end-of-run
  message is branched so the council-off brief path does not claim council
  verdicts. The brief PRD is kept distinct from .loki/generated-prd.md so it
  does not pollute the v7.8.1 generated-PRD-reuse signature.
• Council: 3-of-3 unanimous (first round). No duplication; existing PRD/issue/
  no-arg flows unchanged.