fix(core): bound default search results

[kitlangton]

What

Give V2 filesystem glob and grep searches the same 100-result default bound as V1 when callers omit limit.

The audit found both model-facing search tools had the same unbounded fallback. Other built-in tools already have concrete capture limits: read bounds lines and bytes, shell bounds captured output, and webfetch / websearch bound response sizes.

Before / After

Before: A model could call glob or grep without limit. The tool translated that omission to Number.MAX_SAFE_INTEGER, and the ripgrep adapter collected matching rows in memory. A broad search over a large worktree could therefore retain millions of paths or matches, exhaust process memory, and leave the tool call running indefinitely.

After: Omitted limits resolve to 100 before either ripgrep or fff executes. Ripgrep's existing take(limit + 1) boundary stops collection and terminates the scoped subprocess once the bounded result is known.

How

• packages/core/src/filesystem.ts defines the shared DEFAULT_SEARCH_LIMIT.
• packages/core/src/tool/glob.ts and packages/core/src/tool/grep.ts apply and advertise that default for model calls.
• packages/core/src/filesystem/search.ts applies the same default in both ripgrep and fff service implementations so non-tool consumers cannot recover the unbounded omission behavior.
• packages/core/test/tool-search.test.ts executes both real registered tools against 101 matches and verifies omitted limits settle with 100 structured results.

Scope

This does not change explicit caller-supplied limits or the Location file indexer, whose catch-all scan deliberately uses separate indexing behavior. It does not modify V1, which already hard-codes a 100-result bound for both tools.

Testing

• cd packages/core && bun run test test/tool-search.test.ts (3 passed)
• cd packages/core && bun run test (1,292 passed, 6 skipped)
• cd packages/core && bun run typecheck
• Pre-push hook: bun turbo typecheck --concurrency=3 (32 packages passed)
• bun run prettier --check packages/core/src/filesystem.ts packages/core/src/filesystem/search.ts packages/core/src/tool/glob.ts packages/core/src/tool/grep.ts packages/core/test/tool-search.test.ts
• bun run lint (passes with existing repository warnings)
• bun run lint:effect-patterns remains blocked by seven pre-existing findings outside this diff