Update Claude ACP package name from `claude-code-acp` to `claude-agent-acp`

[glishijie]

Description

The codebase currently references the Claude ACP agent process using the outdated name claude-code-acp, but the latest package has been renamed to claude-agent-acp. This affects both the npm package reference and internal identifiers.

Current State

The following locations use the old naming:

1. NPM package reference (agents.rs:609):

   let package = fallback_npx_package(
       "@zed-industries/claude-code-acp",
       options.agent_process_version.as_deref(),
   );

2. Agent process registry ID (agents.rs:81):

   AgentId::Claude => Some("claude-code-acp"),

3. Agent process binary hint (agents.rs:93):

   AgentId::Claude => Some("claude-code-acp"),

4. Documentation references:

   • research/acp/spec.md:170
   • research/acp/acp-notes.md:59
   • research/agents/claude.md:18

Expected State

All references should be updated to use claude-agent-acp:

• NPM package: @zed-industries/claude-agent-acp
• Registry ID: claude-agent-acp
• Binary hint: claude-agent-acp
• Documentation: Updated to reflect the new name

Impact

This naming mismatch may cause:

• Agent installation failures when using the outdated package name
• Confusion for developers working with the codebase
• Potential runtime errors if the old package is deprecated or removed

Proposed Solution

1. Update the npm package reference in server/packages/agent-management/src/agents.rs:609
2. Update agent_process_registry_id return value for AgentId::Claude
3. Update agent_process_binary_hint return value for AgentId::Claude
4. Update all documentation references to use the new naming
5. Consider adding a deprecation notice or migration guide if needed

Additional Context

The correct package name @zed-industries/claude-agent-acp aligns with the naming convention used by other agents in the system (e.g., cursor-agent-acp).

[linear]

RVT-6010