feat: breadcrumb fallback for post-exit agent detection (#3)

When an agent session is closed before the human runs `git commit` or
when the command is run from a separate terminal, live process detection
may not find the right co-author. This is at present a common "agent
finishes work, human reviews, then commits" flow on laptops.

So as a solution, this PR proposes a breadcrumb fallback process. If
live detection fails, the code will check agent state files already on
disk.

This currently two agents but more can be supported through config
changes :

- **Claude Code** — scans `~/.claude/projects/` for recent `.jsonl`
files with a `cwd` matching the repo
- **Codex** — scans `~/.codex/sessions/` the same way

Rest of the agents can be added after testing. 

**NOTE** This is a heuristic based approach and so its imperfect, but
will improve attritbution. To improve accuracy, the code only ever looks
back ~2 hrs and for sessions that worked on the same folders.

We could have also check if the files being edited in the session match
the session but I found this to slow down git commits by 200%. It wasn't
noticeable on my laptop but may not work as well on other hardware. It
also creates a stronger dependency on vendor session files and paths
that may change in future, so I've left it out for now.

## Test run (from a terminal with no agent in the process tree)

```
....
=== Breadcrumb Fallback ===
  Claude Code breadcrumb dir: /Users/rishibaldawa/.claude/projects
    ...aittributor/224254e5-...jsonl cwd: /Users/rishibaldawa/Development/aittributor
  Codex breadcrumb dir: /Users/rishibaldawa/.codex/sessions
    ...rollout-2026-02-12T06-06-09-...jsonl cwd: /Users/rishibaldawa/Development/aittributor
Claude Code <noreply@anthropic.com>
Codex <noreply@openai.com>
```


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

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: baldawarishi

.gitignore

@@ -1 +1,2 @@
 /target
+.hermit/