docs: bring the syntax reference up to 2.7.3, and surface it where people download

[PathGao]

Three things, all documentation.

1. samples/markdown-syntax.md catches up with 2.7.3

Nothing in the release changed what renders, so the compatibility table is untouched — 25 PRs and not one of them adds or removes a spelling. What changed is behaviour, and five of those are demonstrable on the page itself:

Landed in 2.7.3	Where it goes
Edit jumps to the right-clicked fragment (#539)	§17, first bullet — with ⌘E carrying the selection
Split-view sync by source line (#541)	§17
Sticky scroll (#555)	§17
The unpinned outline gets out of the way (#545)	§17, folded into the existing outline bullet
CJK word-wise navigation, IME space no longer boxed (#546)	§15, where the CJK samples already are

The outline line is written from what f29928a actually does — it collapses when you pick an entry, and when you reach past it to touch what it was covering — rather than from the shorter "steps aside" the commit subject suggests.

Checked and deliberately left alone: Copy Reference still writes in the document's own spelling (preferredReferenceStyle is unchanged), heading completion and task checkboxes were already described correctly. Encoding (#544), line endings (#540), the clipboard rewrite (#548, #551) and the load-race fixes (#552, #553) are not syntax and are not on this page.

Both language versions kept in step.

2. The document is findable now

It was one link in the nav and one clause inside a Features bullet. It now has its own section between Download and Installation from source, in both READMEs and in the generated release body.

• The raw URL comes first. The primary action is downloading the file; reading it on GitHub is the fallback offered in parentheses. The document is built to be opened in Markpad — the preview shows each feature working and the editor beside it shows how each one is written, which is the whole point and the one thing GitHub cannot do.
• It suggests handing the file to an AI. It is a complete list of what renders, so an assistant can reformat a document you already have or write a new one that uses the whole range, and you open the result in Markpad.
• ## Markdown support is gone. In a README that word means the help desk. ## What Markpad renders says what the section is and does not collide with ## Features, which is already "what Markpad can do".

Release-body links are pinned to v${VERSION}, so each release points at the document as it shipped.

3. Both platform notices are generated, not pasted

The Windows SmartScreen notice has been added to the release body by hand every time — the workflow never produced it. It is in the generator now, unchanged word for word, so:

⚠️ It must no longer be pasted in by hand, or it will appear twice.

Beside it, a macOS Gatekeeper notice for what #209 costs a new user:

• The unnotarized .dmg is refused on first launch, and the dialog offers only Cancel and Move to Trash — no way forward from that window.
• Control-click → Open comes first, because it is one step. The System Settings → Privacy & Security → Open Anyway route is second, for people who already hit Cancel.
• It names the consequence that gets reported as a separate bug: unsigned means macOS grants file access per prompt rather than remembering it, so the dialogs repeat — most visibly with auto-save on (turn it off in Settings; closing a tab still offers to save) and in documents with many local images, which can ask once per image.
• Links to the self-signing workaround in #209, noting it has to be redone after each update.

Verification

build.yml parses, and the body-composition step was extracted and run locally against VERSION=2.7.3: the two notices, the table and the new section all render as intended, with no quoting damage from the echo lines. No code paths touched, so no test run is implied.

🤖 Generated with Claude Code