[Feature Request] Persistent session names and colors with settings.json defaults

Bug Description
Feature request: persistent session name + color

Currently /rename and /color set in-memory state that is lost on /clear and
on session restart. There is no way to configure defaults via settings.json,
and SessionStart hooks cannot invoke slash commands.

Proposal: support defaultSessionName and defaultSessionColor in
~/.claude/settings.json (and project-level overrides). Bonus: allow
defaultSessionName to accept a template like "{repoName}" so each project
gets its own label automatically.

Use case: I work across multiple repos and color-code sessions to tell them
apart at a glance. Today I re-type /rename <repo> and /color <x> after every
/clear, which adds friction to a workflow that should be invisible.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.140
• Feedback ID: 64c13a47-dca6-4c26-aa5f-99fef5f74ea1

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/gabrielandrade/.local/share/claude/versions/2.1.140 (expected in multi-process scenarios)\n    at g16 (/$bunfs/root/src/entrypoints/cli.js:2672:2257)\n    at RLH (/$bunfs/root/src/entrypoints/cli.js:2672:1337)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-13T04:23:05.244Z"},{"error":"Error: Request was aborted.\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:51:6192)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-05-13T04:25:20.185Z"}]