flatten: move poc-memory contents to workspace root

No more subcrate nesting — src/, agents/, schema/, defaults/, build.rs
all live at the workspace root. poc-daemon remains as the only workspace
member. Crate name (poc-memory) and all imports unchanged.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/util.rs

@@ -0,0 +1,72 @@
+// Shared utilities
+
+use crate::store;
+
+use serde::de::DeserializeOwned;
+use serde::Serialize;
+
+use std::fs;
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+/// Ensure a subdirectory of the memory dir exists and return its path.
+pub fn memory_subdir(name: &str) -> Result<PathBuf, String> {
+    let dir = store::memory_dir().join(name);
+    fs::create_dir_all(&dir)
+        .map_err(|e| format!("create {}: {}", dir.display(), e))?;
+    Ok(dir)
+}
+
+/// Truncate text to `max_len` bytes at a char boundary, appending `suffix`.
+/// Returns the original string if it's already short enough.
+pub fn truncate(text: &str, max_len: usize, suffix: &str) -> String {
+    if text.len() <= max_len {
+        text.to_string()
+    } else {
+        let end = text.floor_char_boundary(max_len);
+        format!("{}{}", &text[..end], suffix)
+    }
+}
+
+/// Take the first `n` chars from a string.
+pub fn first_n_chars(s: &str, n: usize) -> String {
+    s.chars().take(n).collect()
+}
+
+// ── JSONL helpers ───────────────────────────────────────────────────
+
+/// Read a JSONL file, deserializing each line. Silently skips bad lines.
+pub fn jsonl_load<T: DeserializeOwned>(path: &Path) -> Vec<T> {
+    let content = match fs::read_to_string(path) {
+        Ok(c) => c,
+        Err(_) => return Vec::new(),
+    };
+    content.lines()
+        .filter_map(|line| serde_json::from_str(line).ok())
+        .collect()
+}
+
+/// Append one record as a JSON line to a file (create if missing).
+pub fn jsonl_append<T: Serialize>(path: &Path, item: &T) -> Result<(), String> {
+    let json = serde_json::to_string(item)
+        .map_err(|e| format!("serialize: {}", e))?;
+    let mut f = fs::OpenOptions::new()
+        .create(true).append(true).open(path)
+        .map_err(|e| format!("open {}: {}", path.display(), e))?;
+    writeln!(f, "{}", json)
+        .map_err(|e| format!("write {}: {}", path.display(), e))
+}
+
+/// Parse a timestamp string to unix epoch seconds.
+/// Handles: "2026-03-05T19:56:00", "2026-03-05T19:56", "2026-03-05 19:56:00", "2026-03-05 19:56"
+pub fn parse_timestamp_to_epoch(ts: &str) -> Option<i64> {
+    use chrono::{Local, NaiveDateTime, TimeZone};
+    let formats = ["%Y-%m-%dT%H:%M:%S", "%Y-%m-%dT%H:%M", "%Y-%m-%d %H:%M:%S", "%Y-%m-%d %H:%M"];
+    for fmt in &formats {
+        if let Ok(ndt) = NaiveDateTime::parse_from_str(ts, fmt)
+            && let Some(dt) = Local.from_local_datetime(&ndt).earliest() {
+                return Some(dt.timestamp());
+            }
+    }
+    None
+}