Copilot memory of prior session history

### Describe the feature or problem you'd like to solve

Copilot tries to re-solve problem it has already solved from scratch

### Proposed solution

When I describe an error I've seen before, Copilot should be able to search prior session history to recognize it rather than re-investigating from scratch. A full-text or semantic search index over events.jsonl across sessions would solve this. Currently there's no way to make recurring issues 'stick' in memory except manually maintaining instruction files.

### Example prompts or workflows

Example prompt: "I'm getting this error when launching zsh: compinit:503: no such file or directory:
/usr/share/zsh/vendor-completions/_docker"

Current workflow: Copilot searches the filesystem, reads config scripts, and investigates from scratch — even
though
this exact error was diagnosed and fixed in a prior session. The fix (a one-line sudo rm) already existed as a
documented script in the home directory.

Desired workflow: Copilot searches prior session history for the error string "compinit" or "_docker", finds the
previous fix immediately, and says "we've seen this before — run sudo rm /usr/share/zsh/vendor-completions/_docker"
before doing any filesystem investigation.

What would enable this: FTS or semantic search over events.jsonl across sessions, surfaced automatically when an
error message matches prior conversation history.

### Additional context

_No response_