Merge branch 'buffer-implementation'HEADmain

Establishes the first working baseline: moji <file> opens a file into a
ropey rope and edits it with Helix selection-first modal editing, under a
DO-178C DAL-C requirements and traceability process.

Prior to this, main tracked four files and src/main.rs was still
println!("Hello, world!") — there was no buildable state to build on.

Verified on a fresh clone of the branch with no untracked files:
cargo build; clippy --all-targets -D warnings clean; 294 tests passing;
scripts/check-trace.sh reports 98/98 requirements traced in both
directions.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/logging.rs b/src/logging.rs
new file mode 100644
index 0000000..fd4e0b6
--- /dev/null
+++ b/src/logging.rs
@@ -0,0 +1,36 @@
+use std::sync::LazyLock;
+
+use tracing_error::ErrorLayer;
+use tracing_subscriber::{EnvFilter, fmt, prelude::*};
+
+use crate::config;
+
+pub static LOG_ENV: LazyLock<String> =
+    LazyLock::new(|| format!("{}_LOG_LEVEL", config::PROJECT_NAME.clone()));
+pub static LOG_FILE: LazyLock<String> = LazyLock::new(|| format!("{}.log", config::APP_NAME));
+
+pub fn init() -> color_eyre::Result<()> {
+    let directory = config::get_data_dir();
+    std::fs::create_dir_all(directory.clone())?;
+    let log_path = directory.join(LOG_FILE.clone());
+    let log_file = std::fs::File::create(log_path)?;
+    let env_filter = EnvFilter::builder().with_default_directive(tracing::Level::INFO.into());
+    // If the `RUST_LOG` environment variable is set, use that as the default, otherwise use the
+    // value of the `LOG_ENV` environment variable. If the `LOG_ENV` environment variable contains
+    // errors, then this will return an error.
+    let env_filter = env_filter
+        .try_from_env()
+        .or_else(|_| env_filter.with_env_var(LOG_ENV.clone()).from_env())?;
+    let file_subscriber = fmt::layer()
+        .with_file(true)
+        .with_line_number(true)
+        .with_writer(log_file)
+        .with_target(false)
+        .with_ansi(false)
+        .with_filter(env_filter);
+    tracing_subscriber::registry()
+        .with(file_subscriber)
+        .with(ErrorLayer::default())
+        .try_init()?;
+    Ok(())
+}