feat(logging): add daily log rotation and 7-day cleanup

Logs were growing unbounded — cli.log and server.log used
rolling::never() with no rotation. Switch to daily rotation via
tracing-appender builder API (prefix.YYYY-MM-DD.log) and clean up
files older than 7 days on startup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs-internal/logging-strategy.md

@@ -1,6 +1,6 @@
 # Fabro Logging Strategy
 
-Fabro uses the `tracing` crate for structured, file-based logging. Logs write to `~/.fabro/logs/YYYY-MM-DD.log`, controlled by the `FABRO_LOG` env var (default: `info`). Logs are for **developers debugging issues after the fact** — they are not user-facing output.
+Fabro uses the `tracing` crate for structured, file-based logging. Logs write to `~/.fabro/logs/{prefix}.YYYY-MM-DD.log` (e.g. `cli.2026-04-06.log`, `server.2026-04-06.log`), rotated daily by `tracing-appender`. Logs older than 7 days are cleaned up on startup. Controlled by the `FABRO_LOG` env var (default: `info`). Logs are for **developers debugging issues after the fact** — they are not user-facing output.
 
 Production runs at INFO level. INFO should be low-volume and high-signal — the summary of what happened. When something goes wrong, developers enable `FABRO_LOG=debug` to get the full picture. DEBUG can be as verbose as needed since it's only turned on temporarily.
 

lib/crates/fabro-cli/src/commands/server/start.rs

@@ -169,14 +169,11 @@ fn execute_daemon(
         return Ok(());
     }
 
-    // Rotate logs
     let server_state = Storage::new(storage_dir).server_state();
     let log_path = server_state.log_path();
     if let Some(parent) = log_path.parent() {
         std::fs::create_dir_all(parent)?;
     }
-    let prev_path = log_path.with_extension("log.prev");
-    let _ = std::fs::rename(&log_path, &prev_path);
 
     let record_path = server_state.record_path();
     let log_file = std::fs::File::create(&log_path)?;

lib/crates/fabro-cli/src/logging.rs

@@ -1,8 +1,12 @@
+use std::path::Path;
+
 use anyhow::{Context, Result};
 use fabro_util::run_log;
 use tracing_appender::rolling;
 use tracing_subscriber::{EnvFilter, fmt, layer::SubscriberExt, util::SubscriberInitExt};
 
+const LOG_RETENTION_DAYS: u32 = 7;
+
 pub(crate) fn init_tracing(
     debug: bool,
     config_log_level: Option<&str>,
@@ -21,8 +25,14 @@ pub(crate) fn init_tracing(
     std::fs::create_dir_all(&log_dir)
         .with_context(|| format!("Failed to create log directory: {}", log_dir.display()))?;
 
-    let filename = format!("{log_prefix}.log");
-    let file_appender = rolling::never(&log_dir, &filename);
+    let file_appender = rolling::RollingFileAppender::builder()
+        .rotation(rolling::Rotation::DAILY)
+        .filename_prefix(log_prefix)
+        .filename_suffix("log")
+        .build(&log_dir)
+        .with_context(|| "Failed to create log file appender")?;
+
+    cleanup_old_logs(&log_dir, log_prefix, LOG_RETENTION_DAYS);
 
     let run_log_writer = run_log::init();
 
@@ -44,3 +54,35 @@ pub(crate) fn init_tracing(
 
     Ok(())
 }
+
+fn cleanup_old_logs(log_dir: &Path, prefix: &str, max_age_days: u32) {
+    let cutoff = chrono::Utc::now().date_naive() - chrono::Duration::days(i64::from(max_age_days));
+    let Ok(entries) = std::fs::read_dir(log_dir) else {
+        return;
+    };
+
+    let date_prefix = format!("{prefix}.");
+    let date_suffix = ".log";
+
+    for entry in entries.flatten() {
+        let name = entry.file_name();
+        let Some(name) = name.to_str() else {
+            continue;
+        };
+
+        let Some(rest) = name.strip_prefix(&date_prefix) else {
+            continue;
+        };
+        let Some(date_str) = rest.strip_suffix(date_suffix) else {
+            continue;
+        };
+
+        let Ok(date) = chrono::NaiveDate::parse_from_str(date_str, "%Y-%m-%d") else {
+            continue;
+        };
+
+        if date < cutoff {
+            let _ = std::fs::remove_file(entry.path());
+        }
+    }
+}