Stamp output captured from a package's own process

[rodchristiansen]

A package's stdout was copied into the session log as a single message, so only its first line carried a timestamp and level and every line after it landed as bare text between two properly formatted lines. Now that the log viewer renders stamped lines as event rows, that raw block is the only thing in the file that is not one.

Two changes:

• WriteToFile emits one stamped line per line and drops blank ones. This is the actual defect — any multi-line message had the same problem, not just captured output, so fixing it at the writer means it cannot recur somewhere else.
• Captured output goes through a new WriteCapturedOutput, which tags each line [OUTPUT] <package>: and sends stderr at WARN, so a reader can tell the package's words from BootstrapMate's own. The tag is uppercase in brackets at the start of the message, matching the existing [PROGRESS], [SUCCESS] and [SECTION] tags the viewer renders as pills.

ANSI sequences are stripped — a package writes for a terminal and nothing renders an escape code in a log file.

Verified against the reported case. Feeding the multi-line block from the run that prompted this produces:

[2026-09-02 22:51:00] INFO  [OUTPUT] Preflight System Prep: Starting Chocolatey obliteration process...
[2026-09-02 22:51:00] INFO  [OUTPUT] Preflight System Prep: Removing Chocolatey package manager...
[2026-09-02 22:51:00] INFO  [OUTPUT] Preflight System Prep: Chocolatey removal completed successfully
[2026-09-02 22:51:00] INFO  [OUTPUT] Preflight System Prep: System is now ready for BootstrapMate deployment.

with the blank line dropped. A full run of the built binary produces 18 log lines, 0 unstamped.