docs: normalize page titles and sidebar to sentence case (#3819)

[mvanhorn]

Issue #3819 documented that the docs sidebar and page titles were a mix of title case (e.g. Release History, Success Stories, Topic Guides) and sentence case. The maintainers' chosen approach in the issue thread:

"All titles should be first-word-only capitalized, and the tutorial's sentence-like titles should be replaced with 'real' titles."

This PR does the full sweep: H1 titles, the matching sidebar entries, H2-H4 sub-headings, and tutorial page renames from sentence-like titles to descriptive short titles.

Pages updated

File	Before	After
docs/en/about/releases.md	Release History	Release history
docs/en/about/success.md	Success Stories	Success stories
docs/en/about/roadmap.md	Toga's Road Map	Toga's road map
docs/en/topics/data-sources.md	Data Sources	Data sources
docs/en/topics/index.md	Topic Guides	Topic guides
docs/en/topics/debugging.md	Debugging Your App	Debugging your app

Tutorial titles renamed

File	Before	After
docs/en/tutorial/tutorial-0.md	Your first Toga app	A basic app
docs/en/tutorial/tutorial-1.md	A slightly less toy example	Capturing user input
docs/en/tutorial/tutorial-2.md	You put the box inside another box...	Managing layout
docs/en/tutorial/tutorial-3.md	Let's build a browser!	Building a browser
docs/en/tutorial/tutorial-4.md	Let's draw on a canvas!	Drawing on a canvas

docs/en/tutorial/index.md sub-headings updated to match the renamed tutorials with first-word-only capitalization.

Sidebar (docs/en/SUMMARY.md)

• How-to Guides -> How-to guides
• Internal How-to guides -> Internal how-to guides
• Success Stories, Release History, Toga's Road Map updated to match their pages

Sub-H1 sweep (H2-H4)

~16 sub-headings normalized across 10 files (Backward incompatible changes x10, Future plans, Implementation details, Writing files, Implementing a new backend, etc). Proper nouns preserved (Toga, Qt, Travertino, Pack, CSS, TreeSource, ValueSource). No internal anchor links pointed at the renamed headings.

Other

• docs/en/index.md had a ## [Topic Guides](...) card on the homepage; updated to match.
• Added changes/3819.doc.md per the towncrier convention.

Closes #3819

This contribution was developed with AI assistance (Claude Code).

PR Checklist:

• All new features have been tested
• All new features have been documented

[HalfWhitt]

Hey there, thank you for tackling this.

As a general rule, it's fine for a PR to solve only a (well-scoped) portion of an issue. However, putting "Closes ###" or "Fixes ###" in the top post automatically links the PR and the issue such that merging the PR entirely closes the issue.

Second of all... this is not a particularly vast problem. Incremental progress is generally a virtue, but so far, this is only changing twelve lines. I'd really prefer if you take a stab at the tutorial titles as well — and while it wasn't specifically part of the initial issue, now that you point it out, it would be good to do a sweep for headings below H1 level as well. Would you mind trying that?

[freakboy3742]

One additional detail: when you've used Claude to create this PR, it has removed the PR template that we require on all pull requests. That template has some details that we need contributors to acknowledge. You may need to re-create this PR (or update the PR description) to include that content.

[mvanhorn]

Thanks for the catch - I've updated the PR description to include the checklist template. Apologies for the miss. Let me know if there's anything else you'd like me to adjust.

[mvanhorn]

@HalfWhitt thanks for the review.

• Updated PR description: Closes -> Refs so merge keeps Inconsistent title case in docs #3819 open for the remaining work.
• Tutorial titles (Your first Toga app / A slightly less toy example / etc.) are already sentence-case - no edits needed there.
• Pushed 32b5088 with the H2-H4 sweep: ~16 headings normalized across 10 files (Backward incompatible changes x10, Future plans, Implementation details, Writing files, Implementing a new backend, etc). Proper nouns (Toga, Qt, Travertino, Pack, CSS, TreeSource, ValueSource) preserved. No internal anchor links pointed at the renamed headings.

Let me know if I missed any spots.

[HalfWhitt]

• Updated PR description: Closes -> Refs so merge keeps Inconsistent title case in docs #3819 open for the remaining work.

I'm sorry if I wasn't clear... what I was trying to say was that a) you shouldn't close a ticket if you're not doing all of it, but simultaneously b) I would like you to in fact do all of it, if possible (hence the tutorial titles and subheadings). Therefore, now that you're going for that, it can stay "closes".

• Tutorial titles (Your first Toga app / A slightly less toy example / etc.) are already sentence-case - no edits needed there.

Well, yes, they are, but as you quoted at the top of this PR (emphasis added):

The maintainers' chosen approach in the issue thread:

"All titles should be first-word-only capitalized, and the tutorial's sentence-like titles should be replaced with 'real' titles."

So, for instance, "You put the box inside another box…" would be better titled something like "Managing layout".

Additionally, the links to them from the overall tutorial page don't capitalize the first word, either.

• Pushed 32b5088 with the H2-H4 sweep: ~16 headings normalized across 10 files (Backward incompatible changes x10, Future plans, Implementation details, Writing files, Implementing a new backend, etc). Proper nouns (Toga, Qt, Travertino, Pack, CSS, TreeSource, ValueSource) preserved. No internal anchor links pointed at the renamed headings.

Excellent, thank you 👍

[mvanhorn]

@HalfWhitt got it - thanks for clarifying. Pushed 928d3d3:

• Renamed the tutorial pages to descriptive short titles: A basic app, Capturing user input, Managing layout, Building a browser, Drawing on a canvas.
• Updated the tutorial index page sub-headings and link text to match with first-word-only capitalization.
• Reverted PR description Refs #3819 back to Closes #3819, extended the towncrier note, and combined the H1/sidebar/H2-H4 sweeps under a single scope summary.