fix: accurate --deployment help, aliases, and --list for generate-docs

[u9g]

Stacked on #1033. Addresses review feedback on the docs.livekit.io CLI reference that lk generate-docs produces (livekit/web#6531):

• --deployment on agent delete and agent promote: both used the shared flag, whose help says "Defaults to production". That's wrong for both: agent delete without --deployment deletes the whole agent, including production, and agent promote without it fails with "cannot promote production deployment". Each now has its own flag with accurate help, and promote marks it required, so urfave rejects a missing flag before any API call.
• Command aliases: generate-docs dropped them, so the reference lost lk agent tail and lk agent destroy. Each alias now gets its own usage line, and the options label names both (Options for \logs`/`tail``), matching how the reference wrote them by hand.
• generate-docs --list [command path...]: prints every command below a path that the reference documents: commands that are run, and command groups that take their own options. docs.livekit.io generates one partial per listed command, so new commands appear in its release PR instead of being skipped silently. That's how the reference missed lk agent simulate audio's --background-noise, --low-quality-microphone, and --packet-loss.

How to verify

make build   # or: go build -tags portaudio_system -o bin/lk ./cmd/lk
bin/lk agent delete --help          # --deployment: "If unset, deletes the entire agent, including production."
bin/lk agent promote --id CA_x      # Required flag "deployment" not set
bin/lk generate-docs agent logs     # lk agent logs ... # or lk agent tail ...
bin/lk generate-docs --list agent   # includes agent simulate audio

go test -tags portaudio_system ./cmd/lk/ passes.

[u9g]

lk agent delete --help and lk agent promote --help describing their own --deployment, lk agent promote rejecting a missing --deployment, lk generate-docs agent logs listing the lk agent tail alias, lk generate-docs --list agent listing every simulate subcommand, and lk generate-docs agent simulate audio printing the audio-only flags.

lk-generate-docs-fixes.mp4