Preflight fails on boot: sub_dir default still uses pre-kennel-rename path

[FidoCanCode]

Observed

Second maiden-voyage boot after the _startup_pull fix (#918) merged. Supervisor reaches preflight, then the container exits:

17:45:53 INFO  [supervisor] fido image cache hit fido:local
17:45:53 INFO  [supervisor] starting container image=fido:local
17:45:56 INFO  [-] preflight: all required tools found: git, gh, claude, copilot
preflight: skill-files directory not found: /workspace/src/sub
17:45:56 ERROR [supervisor] container exited code=1 action=fail

Supervisor treats the preflight failure as action=fail and stops (no auto-retry).

Root cause

src/fido/config.py:114 computes the default sub_dir:

sub_dir=Path(__file__).resolve().parent.parent / "sub",

• __file__ = /workspace/src/fido/config.py (in-container)
• .parent = /workspace/src/fido
• .parent again = /workspace/src
• / "sub" = /workspace/src/sub

But the actual sub/ directory is at the repo root: /workspace/sub. So the default path is off by one.

This formula was correct when Fido's Python package lived directly at the repo root (kennel/). The package moved to src/fido/ — one level deeper — so the relative walk back to sub/ now needs to go up one more level. Pure leftover of the rename.

Proposed fix

Change the default to parents[2] / "sub":

sub_dir=Path(__file__).resolve().parents[2] / "sub",

That yields /workspace/sub — which exists and contains persona.md, setup.md, task.md, ci.md, resume.md.

Test plan

• Add a unit test that Config.from_args with default sub_dir points at a directory containing the five canonical sub-skill files.
• Manual: ./fido up clears preflight and reaches starting container-to-worker-up without sub_dir errors.

Why this didn't blow up in CI

CI runs ./fido ci which builds buildx targets but does not exercise run()'s preflight. A dedicated Config default-path test would have caught this.