feat: enhance agent personality, tool guidance, and memory hygiene

- Expand communication style presets (professional, expressive, custom)
- Enrich SOUL.md with human-like tone and emoji-awareness guidance
- Add crash recovery and sub-task scoping guidance to AGENTS.md scaffold
- Add 'Use when / Don't use when' guidance to TOOLS.md and runtime prompts
- Implement memory hygiene system with configurable archiving and retention
- Add MemoryConfig options: hygiene_enabled, archive_after_days, purge_after_days, conversation_retention_days
- Archive old daily memory and session files to archive subdirectories
- Purge old archives and prune stale SQLite conversation rows
- Add comprehensive tests for new features

Cargo.lock

@@ -293,6 +293,17 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "cron"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f8c3e73077b4b4a6ab1ea5047c37c57aee77657bc8ecd6f29b0af082d0b0c07"
+dependencies = [
+ "chrono",
+ "nom",
+ "once_cell",
+]
+
 [[package]]
 name = "crypto-common"
 version = "0.1.7"
@@ -925,6 +936,12 @@ version = "2.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8ca58f447f06ed17d5fc4043ce1b10dd205e060fb3ce5b979b8ed8e59ff3f79"
 
+[[package]]
+name = "minimal-lexical"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
+
 [[package]]
 name = "mio"
 version = "1.1.1"
@@ -936,6 +953,16 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "nom"
+version = "7.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d273983c5a657a70a3e8f2a01329822f3b8c8172b73826411a55751e404a0a4a"
+dependencies = [
+ "memchr",
+ "minimal-lexical",
+]
+
 [[package]]
 name = "nu-ansi-term"
 version = "0.50.3"
@@ -2368,6 +2395,7 @@ dependencies = [
  "chrono",
  "clap",
  "console",
+ "cron",
  "dialoguer",
  "directories",
  "futures-util",