docs(agents): add rule to avoid literal ! in inline Bash commands

Claude Code's Bash tool escapes every ! to \! at the transport layer
(anthropics/claude-code#61121, a regression of a 2.1.87 fix), corrupting
Python !=, jq, Jira JQL, branch names, etc. Documents the single robust
workaround: write !-containing code to .tmp/ via the Write tool and run
the file; .tmp/ is prompt-free via the Edit(.tmp/**) allow rule.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agents/AGENTS.md

@@ -61,6 +61,22 @@ Treat vague input and question-back responses critically, not as instructions.
 - `$TMPDIR` is set by the sandbox to a writable path. `.tmp/` inside the project directory is always writable without prompts.
 - Ensure `.tmp/` is listed in `.gitignore` when creating temp files in a tracked repo.
 
+## Shell — literal `!` in Bash commands
+
+- **Never put a literal `!` in an inline Bash command.** Claude Code's Bash tool
+  escapes every `!` to `\!` at the transport layer before any shell sees it —
+  even inside single/double quotes and in non-interactive shells
+  (anthropics/claude-code#61121, a regression of a fix shipped in 2.1.87). The
+  stray backslash corrupts downstream tools: Python `!=` → SyntaxWarning + broken
+  string, jq, Jira JQL (`status != Done` → server 400), branch names, etc.
+  `bash -c '...'` and quoted heredocs do **not** avoid it.
+- **One rule covers everything:** if a command needs a `!`, write the command/code
+  to a file with the Write tool under `.tmp/` and run the file. `.tmp/` is
+  prompt-free via the `Edit(.tmp/**)` allow rule in `~/.claude/settings.json`. Do
+  **not** create the file with inline `printf`/`echo >` — that re-escapes the `!`.
+- Need a literal `!` inline anyway: ANSI-C hex `$'\x21'` (e.g. `B=$'\x21'; cmd
+  "${B}=…"`) yields a real `!` with no literal `!` in the command.
+
 ## Tooling
 
 - **`ccc` for semantic code search.** Repos containing a