Enhance contribution guidelines and add pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,36 @@
+<!-- Read CONTRIBUTING.md first. An agreed issue is mandatory; PRs without one get closed. -->
+
+## Related issue
+
+Closes #
+
+## What changed
+
+<!-- What it does and how it works. Call out anything non-obvious in the diff. -->
+
+## Memory footprint
+
+<!-- Required. Under 100 MB always, and back to baseline after the palette closes. -->
+
+| Step                    | Memory |
+| ----------------------- | ------ |
+| Idle after launch       |        |
+| Palette open            |        |
+| Feature in use (peak)   |        |
+| Palette closed, settled |        |
+
+Leak-tested:
+
+## Demo
+
+<!-- Visual change → side-by-side before/after video. Same window size, same actions.
+     "After"-only clips and stills don't count. Delete this section if nothing visual changed. -->
+
+## Drawbacks
+
+<!-- Tradeoffs made on purpose, and anything you're unsure about. "None" is a valid answer. -->
+
+## Tests & validation
+
+<!-- Which Tools/ harnesses you ran and any cases you added, plus what you exercised by hand.
+     Commands: docs/development.md § Tests. -->

CONTRIBUTING.md

@@ -26,6 +26,8 @@ Check existing [issues](https://github.com/abue-ammar/tinycast/issues) and
 
 ## Before submitting
 
+- **A linked issue that got a green light.** No agreed issue, no merge — typos and docs-only fixes
+  aside.
 - Builds clean — no new warnings.
 - The `Tools/` harnesses pass; engine changes come with new cases.
 - Leak-tested and memory-measured. Numbers in the PR.
@@ -40,6 +42,8 @@ Check existing [issues](https://github.com/abue-ammar/tinycast/issues) and
 
 ## Pull requests
 
+- Fill in the [PR template](.github/PULL_REQUEST_TEMPLATE.md) — every section, or say why it doesn't
+  apply.
 - **Visual change → side-by-side before/after video. Mandatory.** Same window size, same actions.
   An "after"-only clip doesn't count; stills don't substitute.
 - Non-visual → say what you tested.
@@ -50,7 +54,7 @@ Check existing [issues](https://github.com/abue-ammar/tinycast/issues) and
 
 Match the surrounding code.
 
-- Single-line comments only. Comment the *why*, never the *what*.
+- Single-line comments only. Comment the _why_, never the _what_.
 - Views stay declarative; logic lives in models and managers.
 - Swift 6 isolation — heavy work off the main actor.
 - [`Core/Theme.swift`](Tinycast/Core/Theme.swift) tokens only. Read [`docs/ui.md`](docs/ui.md) before

README.md

@@ -68,9 +68,16 @@ and website workflows, and **[docs/ui.md](docs/ui.md)** for the UI design system
 
 ## Contributing
 
+> [!IMPORTANT]
+> **Open an issue before you write code — this is mandatory.** Get the bug or the feature agreed on
+> first; discussing it in the issue (or on [Discord](https://discord.gg/v2Eeb4QQy3)) is strongly
+> encouraged. A PR with no agreed issue behind it gets closed however good the patch is, and the
+> work is wasted. Typo and docs-only fixes are the one exception.
+
 Read **[CONTRIBUTING.md](CONTRIBUTING.md)** first — it covers the memory budget every PR is held to,
-the before/after video requirement for visual changes, and why features get declined. Security issues
-go through [SECURITY.md](SECURITY.md), not the issue tracker.
+the before/after video requirement for visual changes, and why features get declined. Every PR fills
+in the **[pull request template](.github/PULL_REQUEST_TEMPLATE.md)**. Security issues go through
+[SECURITY.md](SECURITY.md), not the issue tracker.
 
 Questions, ideas, or just want to follow along? **[Join the Discord](https://discord.gg/v2Eeb4QQy3)**.