TASK-166: fix .md preview when Ink hard-wraps a no-space path

[mpmisha]

Problem

When Ink-based TUIs (Copilot CLI, Claude Code) hard-wrap a long .md path that has no embedded spaces, the continuation row starts with Ink's layout indent. The TASK-132/137 seam-space heuristic in TerminalPanel.tsx's .md link provider could not distinguish that indent from a wrap-eaten literal space (as in OneDrive - Microsoft\…), so it always inserted a phantom space at the join — …/files/… became …/fi les/… — fileRead 404'd silently and the preview never opened.

User repro: shrink a terminal pane narrow enough to wrap a .md path printed by a TUI, click the underlined link — nothing happens. DevTools console shows:

[md-link] fileRead returned null { fullPath: '/Users/.../session-state/<id>/fi les/reddit-scout-2026-05-21.md' }

Fix

• Track each inserted seam-space offset during forward and backward hard-newline stitching.
• In activate(), compute a seam-stripped variant of the matched path. Try fileRead on the primary (with-seam) path first; if it returns null and a stripped variant exists, retry. First success drives the markdownPreview overlay.
• Order preserves backward compatibility: legitimate OneDrive - Microsoft\… paths still succeed on the primary attempt.

Tests

Added phantom seam: hard-newline-wrapped no-space path falls back to stripped path on fileRead null to tests/e2e/task-107-md-path-wrap-and-spaces.spec.ts, plus a new installSelectiveFileReadSpy helper that returns content only for the real path. The test asserts both that the primary attempt fires first and that the fallback opens the overlay with the correct path.

Verification

• Typecheck: same baseline (32 pre-existing errors, no new ones).
• E2E: cannot run locally on macOS (suite requires a Windows-packaged build); the new test will validate on CI.
• Manual repro: user confirmed fix before commit.