v0.2.0: installer pipeline (nvim + tmux + opencode)

- guyide install / uninstall / list-backups
- NvGuy editor, tmux multiplexer (TPM bootstrap), opencode agent drivers
- tar.gz backups with manifest tracking
- Auto-writes default config.yaml on first install

v0.1.0: skill-bridge MVP

Initial release of the guyide CLI bridging AI agents and humans to
nvim + tmux + DAP. End-to-end flow verified: set breakpoint, launch
debugpy, hit breakpoint, read locals, continue, stop — all without
the TUI.

Compatible with: nvguy v0.1.0, vscodium.nvim v0.1.0.

Subcommands: version, env, doctor, nvim {status,exec,eval},
tmux {panes,send,watch}, debug {start,stop,continue,step,state,
break set,break clear,list-configs}, layout.

This release is the underlying skill-bridge layer. The installer
(guyide install/update/uninstall, owning ~/.guyide/) ships in v0.2.0.