Suggest optimizing repetitive slow commands

Feature Request

Claude Code should detect and suggest optimizing repetitive slow commands during a session.

Problem

In a long session building an LLVM backend, I ran Docker builds ~50 times. Each invocation included apt-get update && apt-get install -y cmake ninja-build clang lld python3 (~30 seconds). Over the session, this wasted ~25 minutes. I never noticed or suggested caching it in a pre-built Docker image until the user pointed it out.

Expected Behavior

When a Bash command with the same expensive prefix is executed more than 2-3 times, Claude should proactively suggest optimization:

1. Docker: "This docker run installs the same packages every time. Want me to create a cached image?"
2. npm/pip/cargo: "This install step has run N times. Consider caching in a lockfile or pre-built environment."
3. cmake configure: "This configure step is identical to the last run. The build directory already exists."
4. General: Track command prefixes and durations. Flag when cumulative time for repeated patterns exceeds a threshold (e.g., 2 minutes).

Why This Matters

• Users trust Claude to be efficient with their time
• Repetitive setup commands are an obvious optimization that a human developer would spot immediately
• The fix is usually trivial (cache the result) but Claude gets tunnel-visioned on the task and treats infrastructure as boilerplate

Suggested Implementation

Track (command_prefix_hash, duration_ms, count) per session. When count > 3 && total_duration > 60s, suggest optimization. The prefix could be the first N tokens of the command, normalized to ignore variable arguments.