Add -q/--quiet to fabro ps (#64)

Adds a `-q`/`--quiet` flag to `fabro ps`, mirroring the behavior of
`docker ps -q`. When specified, the command outputs only full run IDs,
one per line, with no headers, footers, or "no runs found"
messages—empty output simply means no matching runs exist.

The quiet flag takes precedence over JSON output, and it composes
naturally with other flags like `-a` (e.g., `fabro ps -qa` lists all run
IDs).

### Fabro Details

<details>
<summary>Ran 10 stages in 10m 13s for $1.09</summary>

| Stage | Duration | Cost | Retries |
|---|---|---|---|
| start | 0s | – | 0 |
| toolchain | 0s | – | 0 |
| preflight_compile | 0s | – | 0 |
| preflight_lint | 0s | – | 0 |
| implement | 0s | $0.17 | 0 |
| simplify_opus | 0s | $0.30 | 0 |
| simplify_gemini | 0s | $0.30 | 0 |
| simplify_gpt | 0s | $0.32 | 0 |
| verify | 0s | – | 0 |
| fmt | 0s | – | 0 |
| **Total** | **10m 13s** | **$1.09** | **0** |

</details>

<details>
<summary>Ran <code>ImplementAndSimplify.fabro</code> (13 nodes and 16
edges)</summary>

```dot
digraph ImplementAndSimplify {
    graph [
        goal="Implement and simplify",
        model_stylesheet="
            * { backend: api; model: claude-opus-4-6;}
        "
    ]
    rankdir=LR

    start [shape=Mdiamond, label="Start"]
    exit  [shape=Msquare, label="Exit"]

    toolchain         [label="Toolchain", shape=parallelogram, script="command -v cargo >/dev/null || { curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y && sudo ln -sf $HOME/.cargo/bin/* /usr/local/bin/; }; cargo --version 2>&1", max_retries=0]
    preflight_compile [label="Preflight Compile", shape=parallelogram, script="cargo check -q --workspace 2>&1", max_retries=0]
    preflight_lint    [label="Preflight Lint", shape=parallelogram, script="cargo clippy -q --workspace -- -D warnings 2>&1", max_retries=0]
    fix_lints         [label="Fix Lints", prompt="The preflight lint step failed. Read the build output from context and fix all clippy lint warnings.", max_visits=3]
    implement         [label="Implement", prompt="Read the plan file referenced in the goal and implement every step. Make all the code changes described in the plan. Use red/green TDD."]
    simplify_opus     [label="Simplify (Opus)", prompt="@prompts/simplify.md"]
    simplify_gemini   [label="Simplify (Gemini)", prompt="@prompts/simplify.md", model="gemini-3.1-pro-preview-customtools"]
    simplify_gpt      [label="Simplify (GPT-54)", prompt="@prompts/simplify.md", model="gpt-54"]
    verify            [label="Verify", shape=parallelogram, script="cargo clippy -q --workspace -- -D warnings 2>&1 && cargo nextest run --cargo-quiet --workspace --status-level fail 2>&1", goal_gate=true, retry_target="fixup"]
    fixup             [label="Fixup", prompt="The verify step failed. Read the build output from context and fix all clippy lint warnings and test failures.", max_visits=3]
    fmt               [label="Format", shape=parallelogram, script="cargo fmt --all 2>&1", goal_gate=true, max_retries=0]

    start -> toolchain
    toolchain -> preflight_compile [condition="outcome=success"]
    toolchain -> exit
    preflight_compile -> preflight_lint [condition="outcome=success"]
    preflight_compile -> exit
    preflight_lint -> implement [condition="outcome=success"]
    preflight_lint -> fix_lints
    fix_lints -> preflight_lint
    implement -> simplify_opus -> simplify_gemini -> simplify_gpt -> verify
    verify -> fmt   [condition="outcome=success"]
    verify -> fixup
    fixup -> verify
    fmt -> exit
}

```

</details>

⚒️ Generated with [Fabro](https://fabro.sh)

---------

Co-authored-by: Fabro <noreply@fabro.sh>

lib/crates/fabro-workflows/src/cli/runs.rs

@@ -43,6 +43,10 @@ pub struct RunsListArgs {
     /// Show all runs, not just running (like docker ps -a)
     #[arg(short = 'a', long)]
     pub all: bool,
+
+    /// Only display run IDs
+    #[arg(short = 'q', long)]
+    pub quiet: bool,
 }
 
 #[derive(Args)]
@@ -471,6 +475,13 @@ pub fn list_command(args: &RunsListArgs, styles: &Styles) -> Result<()> {
         },
     );
 
+    if args.quiet {
+        for run in &filtered {
+            println!("{}", run.run_id);
+        }
+        return Ok(());
+    }
+
     if args.json {
         println!("{}", serde_json::to_string_pretty(&filtered)?);
         return Ok(());