feat: additional syntax highlighting — PHP, C/C++, Swift, Terraform/HCL, Dockerfile (v1.7.0)

[shouze]

Context

Part of the 🛠 Developer experience EPIC #77, targeting v1.7.0.

Goal

Extend the regex-based syntax highlighter (src/render/highlight.ts) with five new language profiles. The existing pattern is trivially extensible — each language just needs a new entry in detectLang and a new tokenRules entry.

Languages to add

Language	Extensions	Key tokens
PHP	.php, .phtml	Keywords (function, class, echo…), $variables, strings, comments (//, #, /* */)
C/C++	.c, .h, .cpp, .cc, .cxx, .hpp, .hxx	Keywords (int, void, struct…), preprocessor (#include, #define), strings, comments
Swift	.swift	Keywords (var, let, func, class, guard…), strings, comments
Terraform / HCL	.tf, .hcl	Block keywords (resource, variable, output, module), booleans, strings, # comments
Dockerfile	Filenames matching Dockerfile, dockerfile	Instructions (FROM, RUN, CMD, EXPOSE, ENV…), comments

Acceptance criteria

• Each new language produces ANSI-colored output (ANSI codes present in output)
• Language detection is tested via the detectLang path (extension → tokenizer)
• Dockerfile detection works on filename, not extension
• At least one tokenizer test per language (keyword colorized, comment colorized, string colorized)
• All existing tests still pass