fix(observer): improve Windows compatibility for temp files and Haiku prompt

Address remaining issues from #842 after PR #903 moved temp files to
PROJECT_DIR/.observer-tmp:

Bug A (path resolution): Use relative paths (.observer-tmp/filename)
in the prompt instead of absolute paths from mktemp. On Windows
Git Bash/MSYS2, absolute paths use MSYS-style prefixes (/c/Users/...)
that the spawned Claude subprocess may fail to resolve.

Bug B (asks for permission): Add explicit IMPORTANT instruction block
at the prompt start telling the Haiku agent it is in non-interactive
--print mode and must use the Write tool directly without asking for
confirmation.

Additional improvements:
- Pass prompt via -p flag instead of stdin redirect for Windows compat
- Add .observer-tmp/ to .gitignore to prevent accidental commits

Fixes #842

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Signed-off-by: Lidang-Jiang <lidangjiang@gmail.com>

.gitignore

@@ -83,6 +83,9 @@ temp/
 *.bak
 *.backup
 
+# Observer temp files (continuous-learning-v2)
+.observer-tmp/
+
 # Rust build artifacts
 ecc2/target/