Default paths.graph and paths.samples — no more boilerplate in config.yml

[cweniger]

Summary

• paths.graph and paths.samples no longer need to be declared in config.yml — they default to {run_dir}/graph and {run_dir}/samples
• All three path defaults (graph, samples, buffer) are now applied centrally in _resolve_paths instead of being scattered as or f'{run_dir}/...' fallbacks across call sites
• logging.local.dir removed from example configs (it was being overridden in code anyway)
• paths.graph/paths.samples removed from all four example configs

Changes

• PathConfig.graph: MISSING → Optional[str] = None
• _resolve_paths: applies defaults for all three paths after merge
• api.py _DEFAULT_GRAPH_CONFIG: stripped redundant path/logging keys
• Example configs: paths section now only needs imports

Test plan

• 49/49 existing tests pass
• Smoke-test falcon launch in an example dir without paths.graph/paths.samples in config

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 10.42%. Comparing base (2a7dd8d) to head (b67af3e).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
falcon/cli.py	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #105      +/-   ##
==========================================
- Coverage   10.43%   10.42%   -0.02%     
==========================================
  Files          30       30              
  Lines        3891     3896       +5     
==========================================
  Hits          406      406              
- Misses       3485     3490       +5     

Flag	Coverage Δ
unit	10.42% <10.00%> (-0.02%)	⬇️

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