chore(tasks): add shell efficiency instruction to agent prompts (#68805)

Author: charlesvien

products/tasks/backend/prompts.py

@@ -1,4 +1,11 @@
-WIZARD_PR_AGENT_PROMPT = """
+SHELL_EFFICIENCY_INSTRUCTION = """\
+Shell efficiency: optimize for the fewest shell round trips.
+- Batch related commands into one Bash invocation using `&&` (e.g. `npm run typecheck && npm run lint && npm test`).
+- Emit all independent tool calls in the same response.
+- Read multiple files at once.
+- Never rerun a command solely to reproduce output you already have."""
+
+WIZARD_PR_AGENT_PROMPT = f"""
 PostHog's setup wizard has already run in this repository and integrated PostHog. The working tree
 contains its uncommitted changes (modified source files, an updated package manifest, installed
 dependencies, a `posthog-setup-report.md` summary, and possibly a `.posthog-events.json` plan).
@@ -45,6 +52,8 @@
 full URL (e.g. a Markdown link like [#123](https://github.com/org/repo/pull/123)) rather than plain
 text, so readers can open it directly.
 
+{SHELL_EFFICIENCY_INSTRUCTION}
+
 Hard limits: stay strictly within the wizard's changes, plus the changes required to automatically
 configure the environment variables in production, plus the minimal fixes needed for CI to pass.
 When keeping CI green, do not modify unrelated code, add/remove/upgrade dependencies beyond

products/tasks/backend/temporal/constants.py

@@ -11,6 +11,8 @@
 
 from django.conf import settings
 
+from products.tasks.backend.prompts import SHELL_EFFICIENCY_INSTRUCTION
+
 # Per-task inactivity timeout defaults (production). User-driven runs — explicitly
 # user-created, or with no origin product — get a longer idle grace window since a
 # human may still be in the loop; automated/background runs reclaim the sandbox
@@ -96,7 +98,7 @@ def resolve_inactivity_timeout(*, is_user_origin: bool = False, state: dict | No
 # flush rate-limits retries.
 OUTBOUND_RETRY_BACKOFF = timedelta(seconds=10)
 
-DEFAULT_CI_MESSAGE = """\
+DEFAULT_CI_MESSAGE = f"""\
 You are re-entering this run to address CI feedback on the pull request you opened.
 
 Scope (what to do):
@@ -122,4 +124,6 @@ def resolve_inactivity_timeout(*, is_user_origin: bool = False, state: dict | No
 When you mention the pull request in your summary, always hyperlink it to its full URL (e.g. a
 Markdown link like [#123](https://github.com/org/repo/pull/123)) rather than plain text, so readers
 can open it directly.
+
+{SHELL_EFFICIENCY_INSTRUCTION}
 """.strip()