The command cross-reference regex /^.*`\/(...)`.*$/gm only captured the
LAST command ref per line due to greedy .* consuming earlier refs.
Replaced with line-by-line processing using non-anchored regex to
capture ALL command references.
New tests:
- 4 validate-commands multi-ref-per-line tests (regression)
- 8 evaluate-session threshold boundary tests (new file)
- 6 session-aliases edge case tests (cleanup, rename, path matching)
The test was using 'claude-sonnet-4-5-20250929' which isn't in VALID_MODELS
(haiku/sonnet/opus). Use 'sonnet' with a description field containing
colons to properly test colon handling in frontmatter values.