Extend kbox debugging and system analysis

[Kai5088]

• Add conditional breakpoint framework for GDB
• Add ftrace buffer export mechanism
• Add drgn probing scripts for LKL kernel state
• Add .gitignore for trace artifacts and vendored deps

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Summary by cubic

Adds LKL ftrace tracing (tracer and event modes) with CLI flags and host export, plus GDB and drgn helpers to make kernel debugging easier.

• New Features
  • LKL ftrace tracer mode: enable with --ftrace=function|function_graph, optional --ftrace-filter=SYM, and export with --ftrace-dump=PATH. Mounts tracefs at /.kbox-tracing and clears the buffer before start.
  • Event mode: enable tracepoints via --ftrace-events=cat/ev,... and write results to --ftrace-outdir (creates ftrace.log and start_ts aligned to LKL /proc/uptime).
  • Lifecycle hooks: tracing is set up after boot and automatically dumped on shutdown or error paths.
  • GDB helpers: scripts/gdb/kbox-events.py adds kbox-break-pid and kbox-break-openat for string/struct-aware conditional breakpoints.
  • drgn helper: scripts/drgn/kbox_tasks.py lists LKL tasks (PID/COMM/STATE) for quick state inspection.

^{Written for commit 000080d. Summary will update on new commits.}