fix: preserve markdown hyperlink targets

[kitlangton]

Summary

• Hide Markdown link destinations in conceal mode while keeping visible labels clickable through OSC 8 hyperlink metadata.
• Detect and style visible bare URLs without hyperlinking URLs inside Markdown code spans.
• Preserve distinct markup.link.label and markup.link.url styling.
• Keep generated native chunk styles isolated across live buffers and release transient registrations as buffers/content change.

Before

Check out OpenTUI (https://github.com/sst/opentui) for more.

After

Check out OpenTUI for more.

The displayed OpenTUI label retains its label style and carries the hidden https://github.com/sst/opentui OSC 8 target.

Simplify Review

• Removed the added renderer hyperlink override configuration and TypeScript FFI wiring; terminal capability detection remains the existing source of truth.
• Removed the redundant explicit Markdown-link regex scan; parser URL ranges now walk across intervening conceal highlights to associate labels.
• Limited bare-URL fallback so inline/fenced raw Markdown content is not linkified and parser-provided URL ranges are not duplicated.
• Restored protection for one-character conceal replacements so an entity before a link cannot shift link-range mapping.
• Avoided restyling clickable label text with URL colors when label and URL theme styles differ.
• Replaced per-buffer style registration leakage with cleanup of transient generated styles on content clear/reset, style detach, and buffer destruction.

Verification

• bun test src/lib/detect-links.test.ts passes: 9 pass, 0 fail.
• bun run fmt:check packages/core/src/lib/detect-links.ts packages/core/src/lib/detect-links.test.ts packages/core/src/renderables/Markdown.ts packages/core/src/renderables/__tests__/Markdown.test.ts packages/core/src/renderer.ts packages/core/src/zig.ts packages/core/src/zig/syntax-style.zig packages/core/src/zig/text-buffer.zig packages/core/src/zig/tests/text-buffer_test.zig packages/examples/src/markdown-demo.ts passes.
• zig fmt --check packages/core/src/zig/syntax-style.zig packages/core/src/zig/text-buffer.zig packages/core/src/zig/tests/text-buffer_test.zig passes.
• The previous CI run identified missing link metadata when a conceal range separates label and URL highlights; commit 54a8042a adds that exact regression and the one-line parser-range traversal fix.
• Local renderer/native test execution is blocked by the local Zig linker failure already observed for current clean worktrees; CI builds the native library from source and is the authoritative native verification path.