refactor: extract shared claude session UUID regex

[unni-facets]

The regex matching --session-id <uuid> / --resume <uuid> in a claude argv is duplicated byte-for-byte across 5 files:

• internal/app/sessions.go:19 (claudeSessionArgRe)
• internal/iterm/iterm.go:107 (claudeSessionRowRe)
• internal/terminal/terminal.go:195 (claudeSessionRowRe)
• internal/zellij/zellij.go:134 (claudeSessionRowRe)
• internal/kitty/kitty.go:163 (claudeSessionRowRe)

All five compile the same pattern:

`(?:--session-id|--resume)[ =]([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12})`

Proposed change

Create a new package internal/claudematch exporting:

• the compiled regex
• a small helper like func ExtractSessionUUID(line string) (string, bool) returning the lowercased UUID if a match is found

Update the 5 call sites to import and use it. Behavior must be identical — drop the duplicate vars in each backend.

Notes

• Pure refactor: no behavior change, no contract change, no test rewrites beyond import paths.
• Existing per-package tests should keep passing unchanged.
• Spec-pattern of mock vars (PSRunner, RunnerOutput, etc.) is unrelated and must not be touched.

Acceptance

• go test ./... green
• go vet ./... clean
• No remaining literal copies of the regex outside internal/claudematch