feat: migrate template engine from Stencil to swift-jinja

[alexey1312]

Summary

• Replace Stencil + StencilSwiftKit + PathKit with swift-jinja (HuggingFace) for template rendering across all 4 export modules
• Rename 34 templates .stencil → .jinja with Jinja syntax adaptations ({% include %} → context variables, forloop.last → loop.last)
• Rewrite 4 base exporters from Stencil Environment to renderTemplate() + loadTemplate() with recursive Any → Value conversion
• Update ~27 call sites across 15 exporter files with contextWithHeader() / contextWithHeaderAndBundle() helpers

Dependency impact

Before	After
Stencil, StencilSwiftKit, PathKit*, Komondor, PackageConfig, ShellOut, Spectre	swift-jinja (depends on swift-collections — already present)

Net: −6 packages from the dependency graph

*PathKit remains as transitive dep of XcodeProj

Breaking changes for custom templates

Users with custom templatesPath templates need to:

1. Rename .stencil → .jinja
2. Replace {% include "header.stencil" %} → {{ header }}
3. Replace forloop.last → loop.last (if used)

Test plan

• All 138 tests pass (template outputs verified via string comparison)
• Build succeeds on macOS
• CI passes (Linux build + tests)

🤖 Generated with Claude Code

[gemini-code-assist]

Summary of Changes

Hello @alexey1312, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request undertakes a significant refactoring of the project's templating infrastructure by replacing the Stencil engine with swift-jinja. This migration streamlines template rendering, reduces external dependencies, and modernizes the codebase. The changes involve updating template file extensions, adapting template syntax, and modifying core exporter logic to integrate with the new Jinja-based system, ultimately improving maintainability and performance.

Highlights

• Template Engine Migration: The project's template engine has been migrated from Stencil to swift-jinja across all four export modules (Android, Flutter, Web, Xcode).
• Template File Renaming and Syntax Adaptation: 34 template files were renamed from .stencil to .jinja and their syntax was adapted for Jinja compatibility, including changes like {% include %} to context variables and forloop.last to loop.last.
• Exporter Logic Refactoring: Base exporter classes were refactored to utilize swift-jinja's renderTemplate() and loadTemplate() methods, incorporating recursive Any → Value conversion for context data.
• Call Site Updates: Approximately 27 call sites across 15 exporter files were updated to use new contextWithHeader() and contextWithHeaderAndBundle() helper functions for template rendering.
• Dependency Reduction: Project dependencies were reduced by removing Stencil, StencilSwiftKit, Komondor, PackageConfig, and ShellOut, resulting in a net reduction of 6 packages.
• Breaking Changes for Custom Templates: Users with custom templates will need to rename .stencil files to .jinja and update their include ({% include "header.stencil" %} to {{ header }}) and loop (forloop.last to loop.last) syntax.

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[gemini-code-assist]

Code Review

The pull request successfully migrates the template engine from Stencil to swift-jinja, resulting in a significant reduction of dependencies. The migration includes renaming templates, updating syntax, and rewriting the base exporter logic. My feedback focuses on improving maintainability by reducing code duplication across the four export modules and optimizing performance in loops where templates are repeatedly parsed and rendered. I also noted some minor inconsistencies in error handling and context filtering.