Fix obsidian shell-out to use obsidian-cli instead of obsidian

[ramansrivastava]

Summary

• _obsidian_create() and _obsidian_search() in factory/obsidian/notes.py invoked a binary named obsidian, but the actual obsidian-cli binary is named obsidian-cli. On systems with the real Obsidian desktop app installed (also named obsidian), this launched the GUI app instead, waited out the 10s subprocess timeout, then force-killed it — causing visible window flicker and potential stale SingletonLock files.
• Changed both invocations to use obsidian-cli. If it's not installed, subprocess.run raises FileNotFoundError, which is already caught and falls back to the existing direct file-write path.
• Updated tests/test_obsidian.py::test_write_experiment_tries_cli_first, which had hardcoded the incorrect "obsidian" binary name in its mock/assertion.

Fixes #1460

Test plan

• pytest tests/test_obsidian.py -v — 25 passed
• ruff check factory/obsidian/notes.py tests/test_obsidian.py — clean
• mypy factory/obsidian/notes.py — clean

🤖 Generated with Claude Code

https://claude.ai/code/session_017LiyU9TiqgNaGVu3gWaqE4

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.81%. Comparing base (781194f) to head (c9d0c2d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1474      +/-   ##
==========================================
+ Coverage   82.79%   82.81%   +0.01%     
==========================================
  Files         225      225              
  Lines       24994    24994              
  Branches     4021     4021              
==========================================
+ Hits        20694    20698       +4     
+ Misses       3342     3341       -1     
+ Partials      958      955       -3     

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