fix: improve issue ID prefix extraction for word-like suffixes

Refine ExtractIssuePrefix to better distinguish hash IDs from English
words in multi-part issue IDs. Hash suffixes now require digits or be
exactly 3 chars, preventing "test", "gate", "part" from being treated
as hashes. This fixes prefix extraction for IDs like "vc-baseline-test".

Also updates git hooks to use -q flag and adds AGENTS.md documentation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/templates/hooks/post-checkout

@@ -1,5 +1,5 @@
 #!/bin/sh
-# bd-hooks-version: 0.30.0
+# bd-hooks-version: 0.30.1
 #
 # bd (beads) post-checkout hook
 #

cmd/bd/templates/hooks/post-merge

@@ -1,5 +1,5 @@
 #!/bin/sh
-# bd-hooks-version: 0.30.0
+# bd-hooks-version: 0.30.1
 #
 # bd (beads) post-merge hook
 #

cmd/bd/templates/hooks/pre-commit

@@ -1,5 +1,5 @@
 #!/bin/sh
-# bd-hooks-version: 0.30.0
+# bd-hooks-version: 0.30.1
 #
 # bd (beads) pre-commit hook
 #

cmd/bd/templates/hooks/pre-push

@@ -1,5 +1,5 @@
 #!/bin/sh
-# bd-hooks-version: 0.30.0
+# bd-hooks-version: 0.30.1
 #
 # bd (beads) pre-push hook
 #