Add support for #else and #elif preprocessor directives

[Copilot]

The parser supported #ifndef, #ifdef, #if, and #endif but failed on #else and #elif, causing parse errors on standard C preprocessor patterns:

#ifndef FOO
namespace Primary {
    runtimeclass MyClass { }
}
#else
namespace Fallback {
    runtimeclass MyClass { }
}
#endif

Changes

PEG.js grammar (server/src/midl.pegjs):

• Added elseKW and elifKW keyword definitions following existing preprocessor directive pattern
• Updated preprocessorStatement rule to include both directives

TextMate grammar (syntaxes/midl3.tmGrammar.json):

• Added #elif to preprocessor regex pattern (#else was already present)

Package version (package.json):

• Bumped version from 0.0.32 to 0.0.33

Agent configuration (.github/agents/midl-dev.agent.md):

• Added instructions to always bump package version in future PRs
• Added semantic versioning guidelines
• Updated Agent Responsibilities section with version bumping requirement

Test coverage:

• Added preprocessor.idl validating #ifndef/#else/#endif
• Added preprocessor_elif.idl validating #if/#elif/#else/#endif chains

<issue_title>ifndef not supported</issue_title>
><issue_description>idl > #ifndef FOO > // ... > #else > // ... > #endif >
>
> doesn't seem to be understood.</issue_description>
>
> ## Comments on the Issue (you are @copilot in this section)
>
>
>
>

> Custom agent used: MIDL Language Server Developer
> Expert in MIDL 3.0 language server development, VSCode extensions, and WinRT API definitions

• Fixes ifndef not supported #55

Original prompt

---

This section details on the original issue you should resolve

<issue_title>ifndef not supported</issue_title>
<issue_description>```idl
#ifndef FOO
// ...
#else
// ...
#endif

doesn't seem to be understood.</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

Custom agent used: MIDL Language Server Developer
Expert in MIDL 3.0 language server development, VSCode extensions, and WinRT API definitions

• Fixes ifndef not supported #55

---

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[asklar]

@copilot can you bump the package version? make sure you update the agent description file to do so in future PRs automatically too

[Copilot]

@copilot can you bump the package version? make sure you update the agent description file to do so in future PRs automatically too

Done! Bumped version to 0.0.33 and updated the agent description file with version bumping instructions for future PRs. Changes in commit 5b28c78.