feat(viewer): stay quiet on incomplete/invalid filters while typing

[laurigates]

Problem

jaq runs on each (debounced) keystroke, so a half-typed filter — e.g. ending in | — fails to parse. The result was a raw Debug dump of jaq's internal parser structs flashing in the guide line on nearly every keypress:

jq failed: `jq filter parsing failed: [(File { code: ". | .user | ", path: () }, Parse([(Term, "")]))]`

Two issues: the message is an internal Debug representation, and erroring at all on an incomplete expression (the normal state while typing) is noise.

Fix

run_jaq now returns a typed JaqError:

• Invalid — parse/compile failure (an incomplete or malformed expression, expected while typing).
• Execution — the filter parsed and compiled but failed at runtime (a real problem worth reporting).

The viewer suppresses the guide message for Invalid and leaves the view in place, so typing a multi-stage filter is quiet. Execution errors are still reported, now with jaq's Display message instead of the Debug dump.

Notes

This is a lightweight take on #63 (don't choke on an incomplete expression): it stops the nagging without yet evaluating the longest valid prefix, which would be a larger change. Partially addresses #63.

[laurigates]

Related PRs (no strict merge order) — #120, #121, and #122 are a small series of viewer / status-line improvements that independently edit the same code (refresh_view_with_query in src/json_viewer.rs; this one also touches src/json.rs). They're independent in intent but overlap textually, so whichever merges first, the others will need a quick rebase — no specific order is required.