Tags are links: setting trailing #links apart, and listing pages used as tags

[shovon]

Pb Notes has no tags, and it should stay that way. #Mira, #[[Mira]] and [[Mira]] all name the same page (app/docs/design.md:68, packages/pages/wikilink.ts:23). There is no tag type, no tag record, and no difference in what the three spellings mean. Logseq's DB mode made tags their own kind of thing, and that change is the reason to keep them out.

Still, people write tags. A block often ends in a run of #-spelled links:

Call with the landlord about the boiler #home #todo

Those trailing links are metadata about the block, not part of the sentence, and some people will want them set aside instead of read inline. Some will also want to see every page they use this way.

What stays true

• #Mira and [[Mira]] name one page. Nothing records which spelling was used, and nothing behaves differently because of it, apart from the presentation described below.
• Nothing new goes into the log. Both ideas are views computed from block text that is already there.
• A page used as a tag is an ordinary page: it has blocks, references and properties like any other.

Idea 1: set trailing tags apart when rendering

When a block ends in one or more # links, render them apart from the text: smaller, dimmer, pushed to the end of the line or onto a row of their own. Inline tags in the middle of a sentence (ask #Mira about it) are part of the prose and stay where they are. Editing still shows the raw source.

Idea 2: a list of "tags"

A view listing every page that is referenced at least once with the # spelling, maybe with counts. It's a filter over references, not a category of page. Anyone who wants to treat their tag-pages differently can, and anyone who doesn't never has to see the list.

Open questions

• What counts as "trailing"? Only # links after the last non-link text in the block? Only on the last line? What about trailing [[Mira]] with no #?
• Is "used as a tag" a property of a reference or of a page? If a page is referenced as #Mira once and as [[Mira]] ten times, does it appear in the list?
• Should Idea 1 be on by default or opt-in? Should it also apply in the references cuts under a page?
• Where does the list go: the sidebar, search, or a page of its own? (Not a page called "Tags", which would bring back the thing we're avoiding.)
• The parser already keeps the # in the label (wikilink.ts), so the spelling can be read without any change to the data. Is that enough, or does the reference index need to carry it?