docs: add product roadmap and deferred ideas tracker

Add two planning documents:

- BACKBURNER.md: Tracks deferred ideas including the observation that
  subscription vs API pricing semantics should be modeled separately.
  This acknowledges that Admin Cost API integration is valuable but
  shouldn't be the canonical source for subscription usage analysis.

- CEO_PITCH_DECKS.md: Detailed product pitch for four daemon-enabled
  capabilities: Cognitive Flight Recorder (incident replay), Runaway
  Loop Quencher (active cost containment), Session Archeology Engine
  (behavioral pattern classification), and Latent Tool ROI Scanner
  (tool-level efficiency analysis). Each includes utility analysis,
  feasibility assessment, implementation roadmap, and kill criteria.

These documents capture strategic direction for the daemon infrastructure
being built in parallel.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

BACKBURNER.md

@@ -0,0 +1,10 @@
+# Backburner Ideas
+
+Last updated: February 23, 2026
+
+## Deferred
+
+- Separate pricing semantics for subscription vs API usage:
+  - `cburn` should model Claude subscription economics independently from Admin/API token pricing.
+  - Admin Cost API integration is still valuable for API-key workflows, but should not be treated as the canonical source for subscription usage.
+  - Revisit after daemon/event infrastructure work stabilizes.