deb: drive build_binary_package through the BuildView port

The binary build joins the source build on the reporting ports:
build_binary_package takes a DebBuildOptions struct (replacing eleven
positional arguments), reports target, phases, progress and the
outcome through the environment-agnostic BuildView, and the Phase enum
with its default classifiers moves from the terminal widget into the
deb module (announced through the enter_phase helper). DebUi loses its
inherent event methods and only implements the port; tee logging and
the SIGINT behavior are unchanged.

No behavior change for the CLI; headless consumers pass report::Quiet.

src/report.rs

@@ -21,16 +21,33 @@ use std::sync::Arc;
 use crate::context::LineSink;
 use crate::logfmt::Classifier;
 
+/// Identity of the build whose events follow, as announced through
+/// [`BuildView::target`].
+#[derive(Debug, Clone, Copy)]
+pub struct BuildTarget<'a> {
+    /// Source package name (e.g. `hello`).
+    pub package: &'a str,
+    /// Full version being built (e.g. `2.10-3`).
+    pub version: &'a str,
+    /// What the build targets: a distribution series, optionally with an
+    /// architecture (`noble`, `sid`, `noble/arm64`).
+    pub target: &'a str,
+    /// Whether this is a source-only build (producing a `.dsc`) as opposed
+    /// to a binary build (producing `.deb` files).
+    pub source_only: bool,
+}
+
 /// Observer of a running build: target identification, phases, status
 /// messages, progress and the final outcome.
 ///
-/// Implement this to observe [`crate::build`] flows from any frontend. All
-/// events arrive in order from the build thread; long-lived views are
-/// expected to be `Send + Sync` because builds may run inside async tasks.
+/// Implement this to observe the [`crate::build`] and [`crate::deb`] flows
+/// from any frontend. All events arrive in order from the build thread;
+/// long-lived views are expected to be `Send + Sync` because builds may run
+/// inside async tasks.
 pub trait BuildView: Send + Sync {
-    /// The build target was identified: `package` at `version`, built for
-    /// `target` (a distribution series, optionally with an architecture).
-    fn target(&self, _package: &str, _version: &str, _target: &str) {}
+    /// The build target was identified; the events that follow belong to it
+    /// (including the earliest subprocess output, e.g. a chroot download).
+    fn target(&self, _target: BuildTarget) {}
 
     /// A named phase started (e.g. "Applying patches"). `classifier`
     /// rewrites the phase's raw subprocess lines (see [`crate::logfmt`])
@@ -63,6 +80,12 @@ pub trait BuildView: Send + Sync {
     /// diagnostics it collected through [`BuildView::sink`].
     fn finish_failure(&self) {}
 
+    /// Release the display before writing directly to the shared terminal
+    /// (passthrough diagnostics, cleanup commands that inherit it). The
+    /// release is final for this build; later events may be dropped. A
+    /// no-op for views without a display.
+    fn suspend(&self) {}
+
     /// Whether this view presents build results to the user by itself;
     /// callers use this to fall back to plain-line rendering when it does
     /// not (headless views, verbose mode).