feat: add index markers to DECISIONS.md and LEARNINGS.md templates

New projects will now start with INDEX:START/INDEX:END markers,
allowing the auto-index feature to work from the first entry.

Signed-off-by: Jose Alekhinne <alekhinejose@gmail.com>

Author: josealekhine

.context/TASKS.md

@@ -11,7 +11,7 @@
 
 ## Phase 1.a: Cleanup and Release
 
-- [ ] T1.2.0.1b Add index markers to DECISIONS.md and LEARNINGS.md templates
+- [x] T1.2.0.1b Add index markers to DECISIONS.md and LEARNINGS.md templates
       so new projects start with index structure #priority:low #added:2026-01-29
 - [ ] T1.2.5 feat: implement `--context-dir` global flag to override context directory path
   Documented in cli-reference.md as planned. Should allow `ctx --context-dir /path status`.

internal/templates/DECISIONS.md

@@ -1,5 +1,8 @@
 # Decisions
 
+<!-- INDEX:START -->
+<!-- INDEX:END -->
+
 <!-- Use this format for each decision:
 
 ## [YYYY-MM-DD] Decision Title

internal/templates/LEARNINGS.md

@@ -1,3 +1,6 @@
 # Learnings
 
+<!-- INDEX:START -->
+<!-- INDEX:END -->
+
 <!-- Add gotchas, tips, and lessons learned here -->