report: add BuildView/Prompter ports and drive pkh build through them

Core flows no longer reach into the terminal UI: build_source_package
takes a BuildSourceOptions struct (source tree, domain options, view,
prompter) and reports phases, messages and outcomes through the
environment-agnostic ports in the new report module. The classifiers
move from ui/logfmt to the core logfmt module, DebUi becomes a
BuildView adapter, the re-vendor retry asks the prompter instead of
checking for a TTY, and artifact/success printing moves to the CLI.

Headless consumers pass report::Quiet; an embedding (e.g. a builder
server forwarding events to a web frontend) implements BuildView and
maps the plain-data events onto its own wire format.

src/ui.rs

@@ -3,8 +3,6 @@
 
 /// Live build view for `pkh deb` (status bar + rolling log pane)
 pub mod deb;
-/// Line classifiers rewriting raw subprocess output for the live views
-pub mod logfmt;
 /// Interactive raw-mode prompts: free-text input, option selection and
 /// yes/no confirmation
 pub mod prompt;