docs: add missing fmt, lint, and check command documentation

The CLI has implemented fmt, lint, and check commands since the
beginning, but they were not documented in the README. Users could
only discover these commands through --help output.

Added comprehensive documentation including:
- Usage examples in the quick start section
- Full command reference with all options
- Implementation notes about Deno tool integration
- Config file pattern support (includes/excludes)

These commands wrap Deno's native tools (fmt, lint, check) with
Probitas file discovery, making it easier for users to maintain
their scenario files using familiar Deno tooling patterns.

Author: lambdalisue

README.md

@@ -109,6 +109,15 @@ probitas run --reporter json
 # List scenarios without running
 probitas list
 
+# Format scenario files
+probitas fmt
+
+# Lint scenario files
+probitas lint
+
+# Type-check scenario files
+probitas check
+
 # Show help
 probitas --help
 ```
@@ -184,6 +193,94 @@ probitas init --force
 - `example.probitas.ts` - Example scenario file
 - `probitas.jsonc` - Configuration file
 
+### `probitas fmt [paths...] [options]`
+
+Format scenario files using Deno's formatter.
+
+**Options:**
+
+- `--include <pattern>` - Include pattern for file discovery
+- `--exclude <pattern>` - Exclude pattern for file discovery
+- `--config <path>` - Path to probitas config file
+- `--verbose, -v` - Verbose output
+- `--quiet, -q` - Suppress output
+- `--debug, -d` - Debug output
+
+**Examples:**
+
+```bash
+# Format all scenario files
+probitas fmt
+
+# Format scenarios in specific directory
+probitas fmt api/
+
+# Format with custom pattern
+probitas fmt --include "e2e/**/*.probitas.ts"
+```
+
+**Note:** Runs `deno fmt --no-config` on discovered scenario files. Uses
+includes/excludes from probitas config (same as run/list).
+
+### `probitas lint [paths...] [options]`
+
+Lint scenario files using Deno's linter.
+
+**Options:**
+
+- `--include <pattern>` - Include pattern for file discovery
+- `--exclude <pattern>` - Exclude pattern for file discovery
+- `--config <path>` - Path to probitas config file
+- `--verbose, -v` - Verbose output
+- `--quiet, -q` - Suppress output
+- `--debug, -d` - Debug output
+
+**Examples:**
+
+```bash
+# Lint all scenario files
+probitas lint
+
+# Lint scenarios in specific directory
+probitas lint api/
+
+# Lint with custom pattern
+probitas lint --include "e2e/**/*.probitas.ts"
+```
+
+**Note:** Runs `deno lint --no-config` on discovered scenario files. Uses
+includes/excludes from probitas config (same as run/list). Automatically
+excludes rules: `no-import-prefix`, `no-unversioned-import`.
+
+### `probitas check [paths...] [options]`
+
+Type-check scenario files using Deno's type checker.
+
+**Options:**
+
+- `--include <pattern>` - Include pattern for file discovery
+- `--exclude <pattern>` - Exclude pattern for file discovery
+- `--config <path>` - Path to probitas config file
+- `--verbose, -v` - Verbose output
+- `--quiet, -q` - Suppress output
+- `--debug, -d` - Debug output
+
+**Examples:**
+
+```bash
+# Type-check all scenario files
+probitas check
+
+# Check scenarios in specific directory
+probitas check api/
+
+# Check with custom pattern
+probitas check --include "e2e/**/*.probitas.ts"
+```
+
+**Note:** Runs `deno check --no-config` on discovered scenario files. Uses
+includes/excludes from probitas config (same as run/list).
+
 ## Selectors
 
 Selectors filter scenarios by name or tags: