fix(query): parse field filters inside parentheses

[jojosenthusiast]

Fixes #1074

Reproduction

(sym:foo) was parsed as a literal substring query for sym:foo instead of a grouped symbol filter. ( sym:foo) already parsed as a symbol filter.

Fix summary

• Preserve opening parentheses as parser tokens when the grouped expression starts with a known field prefix.
• Add regression coverage for grouped sym: and f: field filters.

Tests run

• git diff --check → pass
• go test ./query/ -run TestParseQuery -count=1 → pass
• go test ./query -count=1 → pass
• go test ./... -short → fails locally on Windows/environment issues unrelated to query (unix.Umask/platform build errors, missing false, Windows path expectations, struct-size assumptions, allocator memory reserve). The changed query package stayed green.

Risk

Low. The change is limited to tokenization before known field prefixes inside parentheses; non-field parenthesized text keeps the existing literal behavior.

Non-goals

• No broad parser rewrite.
• No changes to non-field parenthesized text behavior.