feat: support global excludes in .bec/rules.yaml

[YasserYG8]

Description:

Describe the Feature

Currently, developers must define exclude paths for each rule individually:

rules:
  - id: no-console-log
    paths: ["**/*.js"]
    exclude: ["node_modules/**", "dist/**", "vendor/**"]
    check: "becwright run forbid --pattern 'console.log'"

  - id: no-debugger
    paths: ["**/*.js"]
    exclude: ["node_modules/**", "dist/**", "vendor/**"]
    check: "becwright run forbid --pattern 'debugger'"

In larger codebases with many rules, this leads to significant configuration boilerplate and duplication. If a new folder needs to be ignored (e.g., build/), the developer has to update every single rule's exclude list.

We should introduce a global_exclude configuration block at the root of .bec/rules.yaml to define ignore patterns globally.

---

Proposed Design

Add support for a top-level global_exclude key in .bec/rules.yaml containing a list of glob patterns:

schema_version: 1

global_exclude:
  - "node_modules/**"
  - "dist/**"
  - "vendor/**"
  - "build/**"

rules:
  - id: no-console-log
    paths: ["**/*.js"]
    check: "becwright run forbid --pattern 'console.log'"

  - id: no-debugger
    paths: ["**/*.js"]
    check: "becwright run forbid --pattern 'debugger'"

---

Execution Flow / Rules Logic

1. During execution, the engine compiles rules and file lists.
2. For each rule, a file is matching if:
   • It matches one of the rule's paths globs.
   • It does not match any of the rule's local exclude globs.
   • It does not match any of the global_exclude globs defined at the file root.
3. Update the YAML schema file (schema/rules.schema.json) to validate the new global_exclude key.