all: s/title/slug/, adjust branch handling

There are two intertwined changes here.

First, replace title with slug, and precommit with commit-message-style.

The slug makes enough of a title, and it provides a single human-readable
identifier we can use everywhere.

Second, construct the branch name on the fly instead of storing it,
out of slug, branch prefix, and retryNumber.
This removes some duplicated data, and makes the retry loop
easier to follow and reason about.
diff --git a/claudetool/about_sketch.txt b/claudetool/about_sketch.txt
index fada880..63ab2e0 100644
--- a/claudetool/about_sketch.txt
+++ b/claudetool/about_sketch.txt
@@ -6,7 +6,7 @@
 ## How to Use Sketch
 - Interact with Sketch by describing what you want it to do or answer.
 - Sketch runs tools and processes your request, mostly autonomously. It provides transparency if you wish to see the details, but you don't have to monitor every step.
-- Changes made by Sketch appear in your original Git repository as a branch named `sketch/<branch-name>` for you to manage like any other branch.
+- Changes made by Sketch appear in your original Git repository as a branch for you to manage like any other branch.
 - You can use both the web UI or CLI interface (use `-open=false` to not automatically open a browser window).
 - Enable browser notifications by clicking the bell (🔔) icon to get notified when Sketch completes its work.
 
@@ -46,7 +46,7 @@
   In the terminal UI, you may prefix any line with an exclamation mark for it to be interpreted as a command (e.g. !ls).
 
 ## Git Integration
-{{ $branch := "foo" }}
+{{ $branch := "sketch/example-branch-name" }}
 {{ if .Branch }}
 NB: In this section, all git commands have been modified to be accurate for this Sketch session.
 {{ $branch = .Branch}}
@@ -57,9 +57,9 @@
 - The UI keeps track of the latest branch it pushed and displays it prominently.
 - You can integrate Sketch's changes using:
   ```
-  git cherry-pick $(git merge-base origin/main sketch/{{$branch}})
-  git merge sketch/{{$branch}}
-  git reset --hard sketch/{{$branch}}
+  git cherry-pick $(git merge-base origin/main {{$branch}})
+  git merge {{$branch}}
+  git reset --hard {{$branch}}
   ```
 - You can ask Sketch to `git fetch sketch-host` and rebase onto another commit.
 - Sketch is good at helping you rebase, merge/squash commits, rewrite commit messages, and other Git operations.