feat: 句中辅助码新增大写字母触发方式 (#620)

* feat(engine): add uppercase trigger for shuangpin mid-sentence helpcode

With the uppercase trigger on, an uppercase letter right after a complete
two-key syllable opens a mid-sentence helpcode block by itself, as if the
backtick had been typed before it: ulpbXihfa is ulpb`xihfa, and a following
uppercase letter is still the second code (ulpbXYih is ulpb`xYih). The raw
input keeps the typed letters; the block rules live in
contracts/mid_sentence_helpcode.h so TSF, Server and engine parse alike,
including the semicolon final, which no longer counts uppercase blocks.

The scheme now hands the parsed layout (source index and decorations) to the
request, so selection advance and preedit no longer re-parse the raw input.
Adds the MidSentenceHelpcodeUppercaseChanged worker opcode (31).

* feat(windows): count uppercase helpcode blocks before backtick and semicolon

With MidSentenceHelpcodeUppercaseChanged on, TSF uses the shared block rules
when deciding whether '`' opens a block and whether ';' is the ing final, in
both the synchronous and the deferred key classification.

* feat(server): wire the mid-sentence helpcode uppercase trigger

New helpcode.shuangpin_mid_sentence_helpcode_uppercase (default off) in both
config templates, both settings hosts and the settings page as a third
trigger checkbox. It takes effect only with mid-sentence helpcode on and
direct helpcode off; the Server applies it to the semicolon final rule and
broadcasts MidSentenceHelpcodeUppercaseChanged to TSF.

engine/direct_helpcode/direct_resolver.cpp

@@ -96,9 +96,9 @@ void apply_spellings(QueryRequest &request, const std::string &typed, const std:
     request.syllable_helpcodes = std::move(helpcodes);
     request.enable_mid_sentence_helpcode = true;
     request.enable_shuangpin_helpcode = false;
-    request.direct_helpcode = true;
-    request.direct_helpcode_source_index = std::move(source_index);
-    request.direct_helpcode_decorations = std::move(decorations);
+    request.has_syllable_helpcode_layout = true;
+    request.syllable_helpcode_source_index = std::move(source_index);
+    request.syllable_helpcode_decorations = std::move(decorations);
     request.valid = !clean.empty();
     if (!request.valid)
         return;