feat(cli): unify exec, queue, run into single 'run' command

Since app is not released, removed old commands entirely:
- Deleted exec.zig (533 lines) - modularized version
- Deleted queue.zig (1248 lines) - complete removal
- Unified all functionality into run.zig

New unified 'ml run' command features:
- Auto-detects local vs remote execution via mode.detect()
- Supports --local and --remote flags to force execution mode
- Includes all resource options: --cpu, --memory, --gpu
- Research context: --hypothesis, --context, --intent, --tags
- Validation modes: --dry-run, --validate, --explain
- Uses modular exec/remote.zig and exec/local.zig for execution

Dispatcher updates (main.zig):
- Removed 'e' (exec) handler
- Removed 'q' (queue) handler
- Updated help text to show unified command

Import cleanup (commands.zig):
- Removed queue.zig import

Total code reduction: ~1,700 lines
All tests pass.

cli/src/commands.zig

@@ -10,7 +10,6 @@ pub const init = @import("commands/init.zig");
 pub const jupyter = @import("commands/jupyter.zig");
 pub const logs = @import("commands/log.zig");
 pub const prune = @import("commands/prune.zig");
-pub const queue = @import("commands/queue.zig");
 pub const run = @import("commands/run.zig");
 pub const status = @import("commands/status.zig");
 pub const sync = @import("commands/sync.zig");

cli/src/commands/run.zig

@@ -201,18 +201,19 @@ fn explainJob(allocator: std.mem.Allocator, job_name: []const u8, options: *cons
 }
 
 fn printUsage() !void {
-    std.debug.print(
-        \\n
-        \\ml run <job_name> [options] [-- <args>]
-        \\
-        \\Unified run command - handles both local and remote execution.
-        \\
-        \\Options:
-        \\  --priority <1-10>       Job priority (default: 5)
-        \\  --cpu <n>, --memory <n>, --gpu <n>   Resources
-        \\  --local, --remote       Force execution mode
-        \\  --dry-run, --validate, --explain     Preview modes
-        \\  --hypothesis, --context, --tags       Research context
-        \\
-    , .{});
+    std.debug.print("Usage: ml run <job_name> [options] [-- <args>]\n", .{});
+    std.debug.print("\nUnified run command - handles both local and remote execution.\n", .{});
+    std.debug.print("\nOptions:\n", .{});
+    std.debug.print("  --priority <1-10>       Job priority (default: 5)\n", .{});
+    std.debug.print("  --cpu <n>               CPU cores requested (default: 1)\n", .{});
+    std.debug.print("  --memory <n>            Memory GB requested (default: 4)\n", .{});
+    std.debug.print("  --gpu <n>               GPU devices requested (default: 0)\n", .{});
+    std.debug.print("  --local                 Force local execution\n", .{});
+    std.debug.print("  --remote                Force remote execution\n", .{});
+    std.debug.print("  --dry-run               Show what would happen\n", .{});
+    std.debug.print("  --validate              Validate job without running\n", .{});
+    std.debug.print("  --explain               Explain what will happen\n", .{});
+    std.debug.print("  --hypothesis <text>     Research hypothesis\n", .{});
+    std.debug.print("  --context <text>        Background information\n", .{});
+    std.debug.print("  --tags <csv>            Comma-separated tags\n", .{});
 }