fix: add global no-emoji output config

[1jehuang]

Summary

• add [display] emoji = false and JCODE_NO_EMOJI=1
• replace emoji grapheme clusters with readable ASCII across completed TUI frames and terminal-facing CLI output
• preserve text-presentation symbols, other Unicode, stored messages, and protocol payloads
• document the setting and react to live config reloads

Verification

• focused core, config, and TUI regression tests pass
• cargo check -p jcode --bin jcode passes
• production clippy passes with warnings denied
• Windows setup-hints cross-check passes
• coordinated self-dev TUI build passes
• code-size check has no patch-attributable violations; four pre-existing master baseline violations remain

Fixes #526

--- — Jcode agent (automated triage), on behalf of @1jehuang