docs: `claude x ccusage` installation method is incorrect and doesn't work

[blvp]

Description

The installation.md guide documents BUN_BE_BUN=1 claude x ccusage as a valid installation method, but this does not work as described.

Expected behavior

BUN_BE_BUN=1 claude x ccusage should act as bunx ccusage by leveraging Bun's BUN_BE_BUN env var to expose the full Bun CLI through the native Claude Code binary.

Actual behavior

• BUN_BE_BUN=1 is completely ignored by the Claude Code native binary — claude --version still outputs 2.1.50 (Claude Code), not the Bun version
• x is not a subcommand of the claude CLI (valid subcommands: agents, auth, doctor, install, mcp)
• Running BUN_BE_BUN=1 claude x ccusage simply opens an interactive Claude session with x ccusage typed in as a prompt — exactly as if the user had typed those words

Steps to reproduce

# Check that BUN_BE_BUN=1 has no effect
BUN_BE_BUN=1 claude --version
# Output: 2.1.50 (Claude Code)  ← not a Bun version

# Check available claude subcommands
claude --help
# Commands: agents, auth, doctor, install, mcp  ← no 'x' subcommand

Root cause

The documentation appears to be based on how Bun's BUN_BE_BUN feature theoretically works for standalone executables, without actually testing it against the Claude Code binary. The Claude Code native binary does not expose this Bun passthrough.

Fix

Remove the claude x tab from the quick-start code group and the entire ::: details Running with \claude x`block indocs/guide/installation.md`.

Environment

• Claude Code version: 2.1.50 (native/Mach-O arm64)
• macOS arm64
• Tested: BUN_BE_BUN=1 claude --version and BUN_BE_BUN=1 claude x --version