feat: add collapsible agent categories and expand/collapse controls

[tejinderpa]

fixes #437

What does this PR do?

This PR improves the sidebar by showing agent categories as collapsible sections instead of displaying every agent at once. It also adds an expand/collapse-all control and prevents browser autofill from inserting saved emails into the sidebar search field.

Type of change

• New agent
• Bug fix
• UI improvement
• Docs update
• Something else (describe below)

Checklist

For every PR:

• I was assigned to this issue before starting
• I have read CONTRIBUTING.md
• This PR is linked to issue [Feature]: Add collapsible agent categories in sidebar #437
• I tested this locally with npm run dev
• No API keys are anywhere in my code
• I did not add any new packages without discussing it first

For new agent PRs:

• I tested the agent with a real API key
• I created a new file in src/agents/definitions/ with the agent config
• The agent id is lowercase and uses kebab-case (like my-agent-name)
• The icon name is from lucide.dev/icons
• The system prompt clearly describes the format of the output
• This agent is not a duplicate of one that already exists

Screenshots (optional — but really helpful for UI changes)

Before:

The sidebar displayed all agents under every category at once, making the list long as more agents were added.

After:

The sidebar now shows categories first. Users can expand a category to see its agents, or use the expand/collapse-all button. The search field also stays empty unless the user types into it.

Anything else I should know?

Verified with npm run build. No new packages were added.

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[mergify]

⚠️ Hey @tejinderpa! It looks like only package-lock.json was changed but package.json was not.
This is usually unintentional — it happens when npm install is run locally with a different npm version.
Please revert the package-lock.json changes by running:

git checkout package-lock.json

Then push again. If you intentionally changed dependencies, make sure package.json is also updated.
— @AditthyaSS

[tejinderpa]

@AditthyaSS merge this one PR

[mergify]

hey @tejinderpa! 👋
Your PR title doesn't follow our required format.
Please update it to:
type: short description
Valid types: feat, fix, docs, style, refactor, test, chore
Example: feat: add sales discovery agent
— @AditthyaSS

[mergify]

hey @tejinderpa! 👋
It looks like package-lock.json was changed but package.json was not.
This is usually unintentional — it happens when npm install is run locally with a different npm version.
Please revert it by running:
git checkout package-lock.json
Then push again. 🙏
— @AditthyaSS

[mergify]

⚠️ Hey @tejinderpa! This PR has a merge conflict that needs to be resolved before we can review or merge it.
Please sync your branch with the latest main and fix the conflicts.
Need help? Check out resolving merge conflicts.
— @AditthyaSS