fix(installer/runtime): honor CODEX_BIN_DIR everywhere

[Microdent]

Summary

Remove runtime and installer assumptions about ~/.local/bin so custom CODEX_BIN_DIR works end-to-end.

Changes

• Installer: PATH export and tmux helper install paths use CODEX_BIN_DIR/BIN_DIR.
• tmux config/scripts: injected bin-dir option and script-relative helper resolution.
• Runtime: resolve helper scripts via CODEX_BIN_DIR and PATH (ccb + completion hooks) instead of hardcoded ~/.local/bin.
• Docs: update troubleshooting text to reference CODEX_BIN_DIR.

Testing

• python -m py_compile ccb bin/ccb-completion-hook lib/completion_hook.py

[Copilot]

Pull request overview

This PR removes hardcoded ~/.local/bin assumptions throughout the codebase to properly honor the CODEX_BIN_DIR environment variable for custom installation paths. It is stacked on top of PR #70 which changes request ID format.

Changes:

• Replaced hardcoded ~/.local/bin paths with dynamic resolution using CODEX_BIN_DIR environment variable
• Added helper functions to locate bin directories and scripts using consistent priority orders (env vars, PATH, defaults)
• Updated tmux configuration to use injected bin directory path via template replacement
• Updated documentation with examples that reference CODEX_BIN_DIR for troubleshooting

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/completion_hook.py	Added dynamic script path resolution using CODEX_BIN_DIR, CODEX_INSTALL_PREFIX, and PATH lookups
lib/ccb_protocol.py	Changed request ID format to 32-hex (from PR #70); added backward-compatible regex patterns
config/tmux-ccb.conf	Added tmux keybindings using @ccb_bin_dir variable; updated comments to reference CODEX_BIN_DIR
ccb	Added _get_bin_dir() and _find_helper_script() helper functions; updated _set_tmux_theme() and _detect_cca() to use dynamic paths
bin/ccb-completion-hook	Updated find_ask_command() and session file search to use CODEX_BIN_DIR and CODEX_INSTALL_PREFIX
README.md	Updated troubleshooting section to reference CODEX_BIN_DIR instead of hardcoded ~/.local/bin
README_zh.md	Updated troubleshooting section to reference CODEX_BIN_DIR instead of hardcoded ~/.local/bin

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[Copilot]

The type annotation Path | None requires Python 3.10+ or the from __future__ import annotations import. The ccb file is missing this import, which will cause a syntax error on Python 3.7-3.9. Add from __future__ import annotations at the top of the file, following the pattern used in other Python files in this codebase (e.g., lib/completion_hook.py, lib/ccb_protocol.py).