docs: add ARCHITECTURE.md contributor guide

[pratyush618]

Adds ARCHITECTURE.md — a contributor-facing map of how the codebase is layered, the boundaries between Rust core / PyO3 bindings / Python API, and the ordered touch-points for common changes (adding a storage method, a Queue method, a contrib integration).

CONTRIBUTING.md now points new contributors to it from the "Making Changes" section.

Three docs, three audiences: end-user architecture docs (behavior), CONTRIBUTING.md (build/test), and ARCHITECTURE.md (code organization).

Summary by CodeRabbit

• Documentation
  • Added a comprehensive architecture document describing the system’s layered structure, boundaries between layers, and key interaction patterns.
  • Provided a system diagram and guardrails to help maintain navigable layering and avoid large-scale rewrites.
  • Included contributor guidance on where to make common changes (storage, feature surface, integrations, serializers).
  • Updated contributor guidelines to recommend reading the architecture doc before making modifications.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1e440e60-c4c3-4607-bd5b-76a326f7e3d7

📥 Commits

Reviewing files that changed from the base of the PR and between 549ae16 and 486ec9d.

📒 Files selected for processing (2)

• ARCHITECTURE.md
• CONTRIBUTING.md

✅ Files skipped from review due to trivial changes (2)

• CONTRIBUTING.md
• ARCHITECTURE.md

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📝 Walkthrough

Walkthrough

This PR adds ARCHITECTURE.md documenting Taskito’s layered Python/Rust architecture, dependency and boundary rules, annotated folder structure, extension recipes for common changes, and scaling guardrails. CONTRIBUTING.md is updated to point contributors to the new guide.

Changes

Taskito Architecture Documentation

Layer / File(s)

Summary

Architecture guide and extension recipes ARCHITECTURE.md, CONTRIBUTING.md

New architecture documentation describes the system layers (Python API surface, PyO3 bindings, Rust core, storage backends, workflows crate, optional native-async support), enumerates dependency/boundary rules (PyO3 seam, asyncio confinement, shared Diesel macros, storage-change coordination), maps repository folders to roles, provides ordered touch-points for adding storage methods, Python/queue features, contrib integrations, and serializers/proxy handlers, and concludes with scaling guardrails. CONTRIBUTING.md now points new contributors to ARCHITECTURE.md.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 I nibble lines and stitch the map so neat,
Layers aligned from Python down to Rust,
A single seam to tie the two and keep,
Recipes for growth and rules to trust.
Hop on—this guide makes contributor steps just.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and clearly describes the main change: adding ARCHITECTURE.md as a contributor guide document.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/architecture-guide

Warning

Tools execution failed with the following error:

Failed to run tools: 14 UNAVAILABLE: read ECONNRESET

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@ARCHITECTURE.md`:
- Around line 29-58: The fenced code blocks containing the ASCII architecture
diagram (the block that begins with
"┌────────────────────────────────────────────────────────────────────────────┐"
and the later block that starts with "py_src/taskito/") are missing a language
tag and trigger markdownlint MD040; edit the ARCHITECTURE.md file to add a
language identifier (e.g., ```text) to both opening fences for those blocks so
they read ```text instead of ``` to silence the lint warnings and preserve
formatting.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 0c44ad32-c91f-4d5e-9dc3-f7517e70eb27

📥 Commits

Reviewing files that changed from the base of the PR and between d2c13b2 and 549ae16.

📒 Files selected for processing (2)

• ARCHITECTURE.md
• CONTRIBUTING.md