fix: prevent catastrophic regex backtracking in _extractImagesFromOutput

[mossgowild]

Fixes #307431

Problem

_extractImagesFromOutput in RunInTerminalTool freezes the renderer main thread for 15–20 seconds on large terminal output. The root cause is a two-step pattern:

1. Line 1291 output.replace(/\r?\n/g, '') strips all newlines, producing a single mega-string.
2. Line 1294 the regex /(?:[^\s]*[\/\\][^\s]*\.(?:png|jpe?g|gif|webp|bmp))/gi has ambiguity — [^\s]* can consume / and \, overlapping with the [\/\\] separator. On a long string the engine explores an exponential number of split-points, causing O(2ⁿ) backtracking.

Profiler evidence: 14/14 renderer-hang samples land on RegExpStringIterator.next inside _extractImagesFromOutput.

Fix

• Process per-line instead of collapsing newlines — file paths never span lines, so collapsing was unnecessary and is the direct trigger of the mega-string.
• Skip lines longer than 10 000 chars — defensive guard against pathological single lines.
• Rewrite regex atoms from [^\s]* to [^\s/\\]* — each atom can no longer consume path separators, making the [/\\] tokens unambiguous and eliminating backtracking entirely.

[justschen]

thanks for taking a look!