Introduce initial implementation of the vmic CLI with PipeWire integration

- Added `Cargo.toml` to define dependencies and project metadata.
- Implemented core CLI functionality for managing virtual microphones (`create`, `edit`, `delete`, `list`, `route`, and `wipe` commands) using `clap`.
- Integrated `rusqlite` for persistent state storage and `pipewire` to manage PipeWire nodes.
- Ensured graceful handling of feedback loops and system defaults during virtual mic creation and deletion.
- Added error handling via `thiserror` for cleaner error definitions.

src/commands/create.rs

@@ -0,0 +1,77 @@
+use crate::cli::CreateArgs;
+use crate::error::{Result, VmicError};
+use crate::pw::{loopback, PwGraph};
+use crate::state::{self, VmicState};
+use crate::ui;
+use std::process::Command;
+
+pub fn run(args: CreateArgs) -> Result<()> {
+    state::require_valid_name(&args.name)?;
+    let name = state::normalize(&args.name);
+    let conn = state::open_db()?;
+
+    if VmicState::exists(&conn, &name)? {
+        return Err(VmicError::AlreadyExists(name));
+    }
+
+    let names = loopback::NodeNames::for_vmic(&name);
+    let graph = PwGraph::connect()?;
+
+    // pw-loopback may steal the default sink/source; restore them afterward.
+    let orig_sink = default_output("get-default-sink");
+    let orig_source = default_output("get-default-source");
+
+    let stages = loopback::create_stages(&graph, &names)?;
+
+    if let Some(sink) = &orig_sink {
+        let _ = Command::new("pactl").args(["set-default-sink", sink]).status();
+    }
+    if let Some(source) = &orig_source {
+        let _ = Command::new("pactl").args(["set-default-source", source]).status();
+    }
+
+    // Insurance: a sink monitor feeding any vmic node is a feedback ring;
+    // it should never exist, but tear it down if one appears anyway.
+    let prefix = format!("vmic_{name}_");
+    let removed = graph.break_feedback_rings(&prefix)?;
+    if removed > 0 {
+        ui::warn(&format!("removed {removed} unexpected monitor feedback link(s)."));
+    }
+
+    let mut state = VmicState {
+        name: name.clone(),
+        sink_name: names.sink.clone(),
+        mid_name: names.mid,
+        mix_name: names.mix,
+        source_name: names.source.clone(),
+        sink_node_id: Some(stages.sink_node_id),
+        mix_node_id: Some(stages.mix_node_id),
+        sink_pid: Some(stages.sink_pid as i64),
+        mix_pid: Some(stages.mix_pid as i64),
+        ..Default::default()
+    };
+
+    if args.loopback {
+        let loop_id = loopback::enable_self_monitor(&graph, &names.sink)?;
+        state.loopback_id = Some(loop_id);
+    }
+
+    state.save(&conn)?;
+
+    ui::ok(&format!("Created virtual microphone '{name}'."));
+    if let (Some(sink), Some(source)) = (&orig_sink, &orig_source) {
+        ui::info(&format!("  Default Output/Input kept intact ('{sink}' / '{source}')."));
+    }
+    println!("  In the source app, set output device to:");
+    println!("    '{}'", ui::blue(&names.sink));
+    println!("  In the receiving app, set input/mic device to:");
+    println!("    '{}'", ui::blue(&names.source));
+
+    Ok(())
+}
+
+fn default_output(subcommand: &str) -> Option<String> {
+    let out = Command::new("pactl").arg(subcommand).output().ok()?;
+    let s = String::from_utf8_lossy(&out.stdout).trim().to_string();
+    (!s.is_empty()).then_some(s)
+}