v0.3.0

The bulk of the v0.2 development line, which landed on main after the early
v0.2.0 tag and had not yet been packaged. A major terminal-UX overhaul plus an
MCP client, project memory, and live model switching.

Added

• Vim modal input editor — a self-built multiline editor (normal / insert /
  visual modes, motions, operators, counts, undo/redo, OSC52 clipboard) that
  replaces rustyline on capable terminals and degrades back to it otherwise.
• Semantic color system — 8 named tokens with truecolor → 256 → 16 → NO_COLOR
  degradation, applied across the header, streaming output, permission prompt,
  help, modal editor, and pager.
• Unified TUI header — a DeepSeek-blue box with an orca mascot and a labeled
  model / cwd / session identity panel; one-line fallback on narrow / non-tty.
• Markdown rendering in the pager (/show, /history) — headings, bold /
  italic / inline code, fenced code blocks, block quotes, lists, links, and
  CJK-aware tables, parsed with pulldown-cmark (behind the tui feature).
• Code syntax highlighting — a hand-rolled zero-dependency lexer highlights
  fenced code blocks and /show of standalone code files; the palette is
  finalized via the design system and tiers across truecolor / 256 / 16.
• @-mention completion — an in-editor popup completes project files and
  directories (gitignore-aware); at submit, @path injects the file content (or
  a directory tree) so the model sees it without polluting the cached prefix.
• Runtime model switching — /model switches the model live, shows it on the
  status bar, and persists the choice to config.toml. An in-editor picker popup
  lists models fetched live from the provider's GET /v1/models, so new models
  appear and retired ones disappear automatically; unknown names are rejected.
• More runtime commands — /sessions, /resume, /new, /compact,
  /init, /tools, plus context-window fill warnings.
• Project memory — AGENTS.md is discovered (walk-up) and injected into the
  REPL / run / issue prompts; /init generates one agentically.
• MCP client — connect to stdio MCP servers and expose their tools alongside
  the built-ins (mcp feature, on by default).
• gitignore-aware search tool and context compaction (/compact).

Changed

• HTTP TLS uses rustls (friendlier for aarch64 cross-compilation).
• bash tool output is capped (32 KiB per stream) to prevent context overflow.

Fixed

• Numerous modal-editor fixes: inline-cursor origin offset, viewport clearing on
  resize / exit, charwise multiline paste, and insert-mode arrow keys.