pretty-table: add Cell struct with per-cell styling and horizontal span

[Copilot]

Adds a Cell type to pretty-table enabling per-cell ANSI styling (bold, italic, fg/bg color) and horizontal column spanning (hspan). Previously rows were [n][]const u8; now they are [n]Cell, with Cell.init(text) as the zero-cost default path.

API changes (src/mod/pretty-table.zig)

• New Cell struct with builder methods: init, span, withBold, withItalic, withFg, withBg, withHspan
• Row(n) is now [n]Cell; plain-text usage wraps strings with Cell.init(...)
• Table gains column_align, padding, and row_separator fields
• Removed cell_colors, header_color, footer_color fields (superseded by per-cell styling)
• Column-width calculation handles multi-column spans in two passes: non-spanning cells first, then expand the last spanned column to fit

Span usage example

const t = Table(3){
    .header = [_]Cell{ Cell.init("Name"), Cell.init("Q1"), Cell.init("Q2") },
    .rows = &[_][3]Cell{
        .{ Cell.init("Alice"), Cell.init("90"), Cell.init("85") },
        // "Total" spans both Q columns; the placeholder Cell.span() fills position 2
        .{ Cell.init("Bob"), Cell.init("On leave").withHspan(2), Cell.span() },
    },
};

Consumers updated

• src/bin/loc.zig: rows and header updated from []const u8 to Cell.init(...) wrappers — no behavioral change
• examples/pretty-table-demo.zig and docs/content/packages/pretty-table.org updated to reflect new API

Scope

src/mod/simargs.zig and all other src/bin/*.zig files are unchanged from the merge base — this PR is strictly scoped to pretty-table.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Improve pretty-table</issue_title>
<issue_description>Reference:

• https://github.com/phsym/prettytable-rs</issue_description>

<agent_instructions>请参考 https://github.com/phsym/prettytable-rs 这个 rust 库的功能，改进我们的 pretty-table 实现，让其功能更加丰富</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Improve pretty-table #20

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[jiacai2050]

能再给表格里的数据加上颜色吗？我看它是支持的

[Copilot]

Pull request overview

This PR performs a major refactoring of both simargs and pretty-table modules. The simargs API is modernized with a ParseOptions struct, renamed fields (args → options, positional_args → positional_arguments, program → program_name), and improved naming throughout. The pretty-table module gains a Cell struct with per-cell ANSI styling (bold, italic, fg/bg colors), column alignment, row separators, and horizontal column spanning (hspan).

Changes:

• Refactored simargs public API: introduced ParseOptions struct, renamed StructArguments to ParseResult, and updated all callers across binaries and examples.
• Enhanced pretty-table with Cell, Color, Align types, column spanning support, and row separators, replacing raw String rows.
• Added TigerStyle coding guidelines skill file and updated documentation.

Reviewed changes

Copilot reviewed 6 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/mod/simargs.zig	Major API refactor: ParseOptions, renamed types/fields, improved naming conventions
src/mod/pretty-table.zig	New Cell/Color/Align types, hspan support, alignment, row separators, extensive tests
src/bin/*.zig	Updated all callers to new simargs API (options, positional_arguments, ParseOptions)
examples/simargs-demo.zig	Updated to new simargs API
examples/pretty-table-demo.zig	Rewritten to showcase new pretty-table features
docs/content/packages/pretty-table.org	Updated docs for Cell API and new features
.agents/skills/zig-tiger-style/SKILL.md	Added TigerStyle coding guidelines
src/bin/loc.zig	Updated to use Cell for table data

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