fix(core): match rule globs against file paths containing spaces

[santhiprakash]

Description

Rule globs like docs/**/*.md or the exact glob docs/foo bar.md silently failed to match files whose names contain spaces, so any rule whose target files lived under e.g. docs/foo bar.md was excluded from the system prompt.

Root cause

core/llm/utils/extractPathsFromCodeBlocks.ts used the regex /([^\s()]+.[a-zA-Z0-9]+)/to pull a filename out of a code-block header. The character class[^\s()] excluded whitespace, so a header like typescript docs/foo bar.md was truncated to just bar.md. The downstream rule matcher never saw the directory portion, so neither the broad glob (docs/**/*.md) nor the exact glob (docs/foo bar.md) could match.

Fix

Replace the regex with a small parser that strips the optional <lang> tag and the optional trailing (<start>-<end>) line range but preserves any spaces inside the path itself. The heuristic for identifying a language tag is that it must be a single token containing no / or \ (paths almost always contain a separator; language tags like typescript, md, py never do).

Tests

• New vitest suite at core/llm/utils/extractPathsFromCodeBlocks.vitest.ts covers paths with spaces (with and without language tag, with and without line range, in nested directories).
• New regression test in core/llm/rules/getSystemMessageWithRules.vitest.ts verifies that docs/**/*.md and the exact glob docs/foo bar.md both apply to a file referenced in a code block.
• Updated existing Jest test core/llm/utils/extractPathsFromCodeBlocks.test.ts with the same regression cases.

Fixes #13135

Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created

Screen recording or screenshot

N/A — backend correctness fix, no UI surface change.

Tests

• core/llm/utils/extractPathsFromCodeBlocks.vitest.ts (new, 9 tests)
• core/llm/rules/getSystemMessageWithRules.vitest.ts (2 new tests added)
• core/llm/utils/extractPathsFromCodeBlocks.test.ts (regression case added)

All pass locally via node_modules/.bin/vitest run in core/. Verified by reverting the fix and re-running: the new regression tests fail on the original code and pass with the fix in place.