refactor(prompt): simplify Buzz agent guidance (#6340)

## Why
The Buzz agent prompt carries verbose agent-draft instructions that add
prompt weight without improving benchmark correctness. Buzz-native
channel trials also showed agents creating permanent channels while
claiming they had applied a one-hour TTL. The static CLI inventory
remains for efficient command discovery by smaller agents.

## What
- Retain the static Buzz CLI command table and direct agents to use
`--help` for full usage
- Compact the owner-reviewed agent-draft guidance without changing its
workflow
- Clarify that `buzz channels create` is permanent unless `--ttl` is
provided

## Benchmark Results
- Terminal-Bench retained 22/22 correctness in the initial no-table
candidate while reducing prompt size, input tokens, tool calls, and
cost; total active time was effectively flat.
- Across two Buzz-native runs, the non-channel cases tied at 26/30; the
CLI clarification directly addresses the observed TTL omission.

## Update — 2026-08-20
- Restored the CLI command table following review feedback about
multistep discovery with smaller agents. The restored-table candidate
has not been re-benchmarked.

Signed-off-by: Salman Mohammed <smohammed@squareup.com>

crates/buzz-acp/src/base_prompt.md

@@ -37,13 +37,9 @@ To assign an issue to someone, run `buzz issues assign --issue <event-id> --repo
 
 ## Conversational Agent Creation
 
-When someone asks to create an agent, ask for at most two things: the agent's name and what it should do day-to-day. Turn the user's rough purpose into the `--system-prompt` yourself; do not separately ask for purpose, tone, constraints, access, runtime, provider, or model unless the user's request is genuinely ambiguous.
+When someone asks to create an agent, ask for at most two things: its name and what it should do day-to-day. Write the `--system-prompt` yourself. Do not ask about runtime, provider, model, credentials, environment variables, or access unless the request is genuinely ambiguous.
 
-`buzz agents draft-create --channel <current-channel-uuid> --display-name <name> --system-prompt <instructions>`
-
-Use the channel UUID from `[Context]`. Do not ask about runtime, provider, model, credentials, environment variables, or access: Buzz Desktop resolves local runtime/provider/model defaults and new agents default to owner-only access. The command only opens a reviewable draft in the owner's Desktop; never claim the agent exists until the owner saves it.
-
-For explicit changes to an existing personal agent, use `buzz agents draft-update --help`. Draft updates also require owner review and save.
+Open an owner-reviewed draft with `buzz agents draft-create --channel <current-channel-uuid> --display-name <name> --system-prompt <instructions>`, using the UUID from `[Context]`. Never claim the agent exists until the owner saves it. For explicit changes to an existing personal agent, use `buzz agents draft-update --help`.
 
 ## Communication Patterns
 

crates/buzz-cli/src/lib.rs

@@ -582,8 +582,9 @@ pub enum ChannelsCmd {
         /// Channel description
         #[arg(long)]
         description: Option<String>,
-        /// Make the channel ephemeral: lifetime in seconds. The relay archives
-        /// it once this many seconds pass without a new message.
+        /// Make the channel temporary/ephemeral: idle lifetime in seconds. If
+        /// omitted, the channel is permanent. The relay archives it once this
+        /// many seconds pass without a new message.
         #[arg(long, value_name = "SECONDS")]
         ttl: Option<i64>,
         /// Apply a desktop-local channel template by name (case-insensitive):