feat(tui): color heredocs in bash commands in their own language - #54705

The bash tool's command was the one block of code in a session drawn as
plain text, while write, edit and apply_patch already go through
tree-sitter. It is now the same `<text>$ command</text>` as before, with
each token a colored span, so it wraps, indents and fits the block
exactly as the plain command does; only the colors differ.

The text appears plain at once and takes its colors when the parser
worker answers. Highlighting goes through a cache keyed by language and
content (packages/tui/src/util/highlight-cache.ts), so a remounted
transcript or a reopened session does not reparse every command.
Identical concurrent requests share one round trip, a failed one is
retried, and the cache holds at most 1000 entries or 4M characters.

In the transcript red means a failed or rejected tool call, so the
command is colored with a syntax style that never uses red
(packages/tui/src/theme/tool-code.ts): every syntax slot that comes out
red, or in the theme's error color, takes a non-red alternative, such as
the function color for variables, commands and builtins. A test checks
every built-in theme in dark and light.

nvim-treesitter's bash query narrows its number, constant and shebang
captures with `#lua-match?`, which web-tree-sitter does not evaluate, so
every word came back as a number and every variable as a constant.
packages/tui/src/util/bash-highlight.ts applies those patterns after the
worker answers. It also drops the query's `@spell` captures: the theme
colors spell as plain text, which turned every comment back to the text
color.

`syntax.bash: false` in tui.json restores the plain-text command.

A heredoc body in a bash command is colored as one shell string, though
it is usually a whole program: Python fed to `python3 -`, SQL to
`psql`, a TypeScript file written with `cat > x.ts`. tree-sitter-bash
marks the body but not its language, and opentui's injection mapping
only maps fixed node types, so the language comes from the command
that reads the body (packages/tui/src/util/heredoc.ts):

- python/uv -> python, node -> javascript, bun/deno/tsx -> typescript,
  ruby/bundle/rails -> ruby, perl, php, lua
- sqlite3/psql/mysql/mariadb/duckdb/clickhouse-client -> sql
- jq/curl -> json, kubectl/yq -> yaml, bash/sh/zsh/ssh -> bash
- git commit/gh/glab -> markdown, git apply/patch -> diff
- cat/tee to a file -> the file's language by extension
- a command behind sudo, env, timeout, ssh, docker exec or kubectl
  exec counts as the command it runs; `cat <<EOF | psql` as psql
- otherwise a #! line on the body, otherwise nothing: an unknown body
  keeps the shell's string color rather than a guess

After the worker colors the command as bash, each body with a known
language is highlighted on its own, through the same cache, and its
highlights replace bash's string color on that range. A language
without a parser, or a failed request, leaves the bash coloring.
Bodies use the same non-red syntax style as the command.

`syntax.heredoc: false` in tui.json keeps every body a shell string.