Preserve plugin-resolved results in exact match mode

[multiplex55]

Motivation

• Exact-mode post-filtering was removing plugin-resolved concrete results (e.g. note:new:*, note:open:*) when a plugin had already resolved a command like note today or note search <term>.
• The launcher should still apply exact matching for pure command-suggestion contexts (e.g. query:* actions) while avoiding re-filtering of plugin-side search/transform outputs.

Description

• Add helper fn should_bypass_exact_post_filter(query: &str, action: &str) -> bool to detect explicit plugin commands and non-query: actions that should bypass exact-mode display-text post-filtering.
• Apply the bypass inside search_plugins in both exact-mode branches, including the g web-search branch and the general plugin_results branch that uses query_term_lc.
• Preserve exact-match behavior for suggestion-only actions by keeping query:* actions participating in the normal exact display filtering.
• Add inline comments explaining why plugin-resolved outputs (e.g. note today, note search <term>) must not be re-filtered by the launcher's label/description exact matching, and add a small test plugin plus exact_mode_keeps_plugin_resolved_results_but_filters_query_suggestions to validate behavior.

Testing

• Ran cargo fmt --check which succeeded.
• Attempted cargo test exact_mode_keeps_plugin_resolved_results_but_filters_query_suggestions -- src/gui/mod.rs but the build failed in this environment due to a missing system dependency (alsa / alsa.pc) required by the alsa-sys crate invoked during the test build, so the new test could not complete here.
• Confirmed the code compiles locally up to the system-dependent build step; the change is limited and covered by the added unit test which should pass once the test environment has the required system dev libraries (pkg-config + alsa development files).

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Codex Task