fix(render): wrap URLs in OSC 8 hyperlinks for clickable terminal links

[shayne-snap]

Summary

Glamour's word-wrap breaks long URLs at hyphens, inserting newlines and padding that truncate the URL from the terminal's autodetection. This PR adds a post-processing step that wraps http(s) URLs in OSC 8 escape sequences so terminal clicks resolve to the full URL.

Changes

internal/tui/render/markdown.go

• injectHyperlinks — post-processes glamour's ANSI output to reconstruct URLs broken across wrap gaps ([spaces]\n[spaces]) and wraps them in OSC 8 hyperlinks
• markCodeURLs — marks http(s):// occurrences inside fenced/inline code blocks with a zero-width marker so they remain literal (no clickable link for code URLs)
• urlSkipMark (0x1c, FS control byte) — preserved through glamour as zero-width, stripped in final output
• scanWrappedURL / shouldJoinWrappedURL — heuristic to join glamour-wrapped URL fragments across lines
• shouldTrimURLTail — trims trailing punctuation (.,;:!?) and unbalanced closers from click targets
• Error fallback path now also runs injectHyperlinks on raw input

internal/tui/render/chat_test.go

• Updated URL duplicate-counting assertions to use xansi.Strip(got) so ANSI escape sequences from OSC 8 wrapping don't cause false negatives

internal/tui/render/markdown_hyperlinks_test.go (new)

• Tests for injectHyperlinks: wrap across lines, no over-join, punctuation trimming, balanced delimiters, no-op passthrough, multiple URLs

Testing

• Existing tests pass with the xansi.Strip adjustments
• New tests cover the core scenarios