fix: write Alt+Enter through zellij as CSI-u

[filipeforattini]

Why

red-dev runs zellij with support_kitty_keyboard_protocol false, so zellij forwards Alacritty's Alt+Enter to the pane as a bare ESC CR. Pane apps cannot tell that apart from Escape followed by Enter, or from the ESC CR some terminals send for Shift+Enter (see redcode PR #449's analysis). Shift+Enter and Ctrl+Enter already avoid this by having zellij write their CSI-u sequence.

What

• config/zellij/config.kdl: in the shared_among "locked" "normal" block, bind "Alt Enter" { Write 27 91 49 51 59 51 117; } (ESC[13;3u: 13 = Enter, 3 = 1 + alt bit).
• config/bash/inputrc.conf: "\e[13;3u": "\C-q\C-j", so bash inserts a newline and never echoes raw bytes. This keeps the old behavior: inside zellij the prompt is owned by ble.sh, which binds M-C-m/M-RET to newline and decodes CSI 13;3u natively as M-RET (checked in the installed ble.sh). Plain readline had ESC CR unbound, so it now matches ble.sh.
• src/dotfiles.ts: new shipped hash (d72b81…) added to SHIPPED_ZELLIJ_CONFIGS. The 1.0.169 base (dc5ea3…) was already listed, so untouched configs upgrade, both bare and under the Linux desktop's generated clipboard tail. Machines with a config.user.kdl layer (composed configs) are regenerated on every converge anyway.
• Tests: new src/alt-enter.test.ts (zellij binding in the shared block, survives a user layer, inputrc mapping). src/zellij-config-upgrade.test.ts pins that the 1.0.169 config is dc5ea3… and upgrades, and the HOME-independent test now also strips the Alt+Enter paragraph.
• README: one paragraph in the input-gestures section.

Agents: what they receive now

Claude Code and Codex now receive CSI 13;3u for Alt+Enter instead of ESC CR.

• Codex (crossterm): crossterm always decodes CSI-u, even without the kitty flags pushed, and turns 13;3u into Enter + ALT. It decodes ESC CR into the same KeyEvent, so nothing changes for Codex.
• Claude Code (Ink-based parser): it already receives CSI 13;2u for Shift+Enter through this same zellij path, so its parser handles the CSI-u format. I did not check that it maps the alt modifier (3) to meta+return. Risk: if it does not, Alt+Enter would stop inserting a newline in Claude Code. Shift+Enter and Ctrl+Enter still work there.
• RedCode: input_newline already lists alt+return, and opentui decodes CSI-u modifiers.

Validation

Ran locally: bun test on alt-enter, zellij-config-upgrade, shift-enter, zellij-layer, terminal-input-stack, clipboard, drift-zellij, emoji, generated-configs-parse and terminal-release (all pass). tsc --noEmit is clean. CI runs the full suite.

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