[docs]: align the AGENTS.md branch-name rule with commit-lint #159

Description

AGENTS.md (Branching and commits) says to use only feature-<id>, bug-<id> or hotfix-<id> branch names; PR #158 merged from docs/agent-trunk-fmt-hook with Validate Branch Name passing. The organization pattern, enforced by this repository's commit-lint.yml caller with the default BRANCH_PATTERN of the reusable workflow, is feature-<issue>, bug-<issue> or hotfix-<issue> with an optional lowercase -<slug>, or <type>/<slug> with a Conventional Commits type (pull-request runbook). Only F-Sy-H narrows it, through a branch-pattern input. Align the text with the enforced pattern, linking the runbook instead of restating a narrower list.

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