fix(search): fall back to TSV when gum table rejects input (#148)

[olavostauros]

Summary

When note titles, body snippets, or metadata contain characters that
gum table cannot parse (tabs, newlines), notes search crashes
with CalledProcessError. This is a presentation-only failure — the
search results are correct. The same bug affects notes list.

Changes

• Sanitize cells: Replace tabs with spaces and newlines with ⏎
  before passing data to gum.
• Fallback: If gum still fails (or is missing), print the results
  as plain tab-separated text instead of crashing.
• --json output is unaffected (bypasses gum entirely).
• Applied same fix to .mise/tasks/list (identical gum table pattern).

Design decisions

Decision	Choice
Missing gum	Soft fallback to TSV, not a hard error
Newline replacement	⏎ is acceptable; --json is the contract for machine consumption
Sanitization timing	After joining final cell value, not per-element
Test tab survival	python3 -c heredoc for reliable literal tab character

Validation

• bats test/search.bats — all 6 tests pass (1 new)
• bats test/list.bats — all 13 tests pass
• git diff --check

Closes #148

[junior-ricon]

Thanks for identifying that a Gum presentation failure should not discard valid search results.

The review repair carries two lessons forward. Shared behavior used by multiple public commands belongs behind one maintained boundary rather than duplicated inline blocks. Fallback tests should also force the dependency failure deterministically; unusual input that sanitization already makes valid does not prove the fallback path. The final coverage exercises failed Gum, missing Gum, sanitized TSV, both list and search, and the JSON bypass.