docs(cli): say what each command does, not how it works

[naliyi]

Follow-on to #61. The descriptions still explained how things work; this makes them say what the command does.

What came out

Mechanism, across the board: the NIP-98 transport the admin subcommands use, "deduplicated by hash", ping's Limit-1 subscription, the config search order, "merged across all targets", "each server downloads it directly; no bytes pass through ncli", "wait for each relay's OK", and the last of the TUI/daemon jargon.

Eight descriptions disappeared entirely once the mechanism was gone and only a restatement of the headline remained: blossom mirror, blossom report, blossom servers, relay, apply, miner, prefs, prefs relays.

ncli relay with no config — the case that started this — is now:

Error: no relay config found; pass --config <file> or --context <name>

Run and operate a Nostr relay

Usage:
  ncli relay [flags]
  ncli relay [command]

Examples:
  ncli relay --config relay.yaml
  ncli relay --context myrelay

The create-if-missing behaviour that appeared twice now lives only on the --context flag.

Headlines

before	after
Reindex a running relay without restarting it	Rebuild a relay's indexes while it runs
Show live relay metrics and worker status	Show live relay metrics
Reattach the TUI to a running bunker daemon	Reattach to a running bunker
Run ncli as a NIP-46 remote signer	Sign other apps' events as a NIP-46 signer
Set (or clear, with "") a trusted app's display name	Rename a trusted app
Revoke one remembered permission, leaving the rest	Revoke one of an app's permissions

Coverage

Checked rather than eyeballed. Walked all 71 user-reachable commands out of the built binary (plus root and the hidden daemon = 73, matching the source count), then:

• scanned every description against a mechanism-wording pattern — one hit remained (bunker), now zero;
• scanned for descriptions restating their own headline — fourteen hits, all resolved by dropping or trimming.

What stays is only what the rest of the help doesn't already show: what the output contains, what the exit code means, and which flags conflict.

Verification

gofmt, go build ./..., go vet ./..., go test -short ./... clean. No test asserts on Short/Long text.