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