* Add debug logging for cmd+click link handling
Logs every decision point in the link opening pipeline:
- mouseDown/mouseUp: modifier keys, click count, position
- resolveTerminalOpenURLTarget: input URL, classification (external/embedded/fallback)
- OPEN_URL action handler: routing decision (cmuxBrowser disabled, external, whitelist miss, embedded browser pane)
All logs are #if DEBUG only via dlog().
* Update tagged build link format for Claude Code cmd+clickability
Claude Code gets a markdown link with the real derived-data path
(file:///tmp/cmux-<tag>/Build/Products/Debug/cmux%20DEV%20<tag>.app)
which is cmd+clickable in cmux. Codex keeps the original format.
* Add equal sign separators to Claude Code build link format
* Fix cmd+click URL buffer overread in OPEN_URL handler
cmux was using String(cString:) to decode the URL from
GHOSTTY_ACTION_OPEN_URL, which reads until a null terminator.
The C struct provides both a pointer and a length field (url + len),
and the pointer is not guaranteed to be null-terminated. This caused
cmux to read past the URL bytes into adjacent memory, producing
corrupted URLs like "https://example.comcom" and multi-URL
concatenations.
Fix: use Data(bytes:count:) with the length field, matching how
vanilla Ghostty decodes the same struct in Ghostty.Action.swift.
* Address review feedback: extract debugModifierString helper
56f184d02e