docs: update differences.md to reflect config parsing and hot reload implementation

differences.md

@@ -12,7 +12,7 @@
 |---------|:--:|:----:|-------|
 | NKey generation (server identity) | Y | Y | Ed25519 key pair via NATS.NKeys at startup |
 | System account setup | Y | Y | `$SYS` account created; no event publishing yet (stub) |
-| Config file validation on startup | Y | Stub | `-c` flag parsed, `ConfigFile` stored, but no config parser |
+| Config file validation on startup | Y | Y | Full config parsing with error collection via `ConfigProcessor` |
 | PID file writing | Y | Y | Written on startup, deleted on shutdown |
 | Profiling HTTP endpoint (`/debug/pprof`) | Y | Stub | `ProfPort` option exists but endpoint not implemented |
 | Ports file output | Y | Y | JSON ports file written to `PortsFileDir` on startup |
@@ -42,7 +42,7 @@
 | SIGTERM | Y | Y | `PosixSignalRegistration` triggers `ShutdownAsync()` |
 | SIGUSR1 (reopen logs) | Y | Y | SIGUSR1 handler calls ReOpenLogFile |
 | SIGUSR2 (lame duck mode) | Y | Y | Triggers `LameDuckShutdownAsync()` |
-| SIGHUP (config reload) | Y | Stub | Signal registered, handler logs "not yet implemented" |
+| SIGHUP (config reload) | Y | Y | Re-parses config, diffs options, applies reloadable subset; CLI flags preserved |
 | Windows Service integration | Y | N | |
 
 ---
@@ -247,7 +247,7 @@ Go implements a sophisticated slow consumer detection system:
 | `-a/--addr` | Y | Y | |
 | `-n/--name` (ServerName) | Y | Y | |
 | `-m/--http_port` (monitoring) | Y | Y | |
-| `-c` (config file) | Y | Stub | Flag parsed, stored in `ConfigFile`, no config parser |
+| `-c` (config file) | Y | Y | Full config parsing: lexer → parser → processor; CLI args override config |
 | `-D/-V/-DV` (debug/trace) | Y | Y | `-D`/`--debug` for debug, `-V`/`-T`/`--trace` for trace, `-DV` for both |
 | `--tlscert/--tlskey/--tlscacert` | Y | Y | |
 | `--tlsverify` | Y | Y | |
@@ -257,10 +257,10 @@ Go implements a sophisticated slow consumer detection system:
 ### Configuration System
 | Feature | Go | .NET | Notes |
 |---------|:--:|:----:|-------|
-| Config file parsing | Y | N | Go has custom `conf` parser with includes |
-| Hot reload (SIGHUP) | Y | N | |
-| Config change detection | Y | N | Go tracks `inConfig`/`inCmdLine` origins |
-| ~450 option fields | Y | ~62 | .NET covers core + debug/trace/logging/limits/tags options |
+| Config file parsing | Y | Y | Custom NATS conf lexer/parser ported from Go; supports includes, variables, blocks |
+| Hot reload (SIGHUP) | Y | Y | Reloads logging, auth, limits, TLS certs on SIGHUP; rejects non-reloadable changes |
+| Config change detection | Y | Y | SHA256 digest comparison; `InCmdLine` tracks CLI flag precedence |
+| ~450 option fields | Y | ~72 | .NET covers core + all single-server options; cluster/JetStream keys silently ignored |
 
 ### Missing Options Categories
 - ~~Logging options~~ — file logging, rotation, syslog, debug/trace, color, timestamps all implemented; only per-subsystem log control remains
@@ -393,15 +393,13 @@ The following items from the original gap list have been implemented:
 - **Subscription statistics** — `Stats()`, `HasInterest()`, `NumInterest()`, etc.
 - **Per-account limits** — connection + subscription limits via `AccountConfig`
 - **Reply subject tracking** — `ResponseTracker` with TTL + max messages
-
-### Remaining High Priority
-1. **Config file parsing** — needed for production deployment (CLI stub exists)
-2. **Hot reload** — needed for zero-downtime config changes (SIGHUP stub exists)
+- **Config file parsing** — custom lexer/parser ported from Go; supports includes, variables, nested blocks, size suffixes
+- **Hot reload (SIGHUP)** — re-parses config, diffs changes, validates reloadable set, applies with CLI precedence
 
 ### Remaining Lower Priority
-3. **Dynamic buffer sizing** — delegated to Pipe, less optimized for long-lived connections
-4. **JWT authentication** — needed for operator mode
-5. **OCSP support** — certificate revocation checking
-6. **Subject mapping** — input→output subject transformation
-7. **Windows Service integration** — needed for Windows deployment
-8. **Per-subsystem log control** — granular log levels per component
+1. **Dynamic buffer sizing** — delegated to Pipe, less optimized for long-lived connections
+2. **JWT authentication** — needed for operator mode
+3. **OCSP support** — certificate revocation checking
+4. **Subject mapping** — input→output subject transformation
+5. **Windows Service integration** — needed for Windows deployment
+6. **Per-subsystem log control** — granular log levels per component