Add semantic code tooltips

FsLiveDocs compiles documentation once during capture and stores renderer-neutral semantic data for later rendering.

How semantic code works

The pipeline uses one expanded documentation model:

Markdown and transclusions
        ↓
stable documentation blocks
        ↓
project compiler evaluation
        ↓
verification cases and semantic results
        ↓
renderer-neutral release capsule
        ↓
current HTML renderer

The stored semantic component contains:

• token text and FsLiveDocs token classifications;
• block-local tooltip references;
• inferred signatures and documentation;
• mapped diagnostics;
• source and page-context hashes;
• the repository documentation prelude.

It does not contain HTML, formatter types, CSS classes, or tooltip DOM IDs.

Use page-scoped blocks

Ordinary F# blocks share one page compilation context:

```fsharp
let add left right = left + right
```

```fsharp
let total = add 20 22
```

The second block can use declarations from the first block.

Add shared setup

Use prepare for setup that later blocks need:

```fsharp prepare
open System
let now = DateTimeOffset.UnixEpoch
```

The setup participates in compilation and source hashing. The renderer displays it as shared setup.

Check a block independently

Use isolated when a block must not share declarations with the page:

```fsharp isolated
let value = 42
```

Select a project

Set project in front matter when a page needs a nondefault project:

---
title: HTTP client
project: src/Example.Http/Example.Http.fsproj
---

Pass every selected project to FsLiveDocs. The command fails and lists the supplied projects when one is missing.

Configure repository setup

Set fSharpPrelude in .livedocs/config.json:

{
  "fSharpPrelude": "open System\nopen Example"
}

FsLiveDocs compiles the prelude for checked pages and stores it in the semantic component.

Understand hash failures

FsLiveDocs hashes each block's normalized source and semantic mode. It also hashes page preparation and other context that can change meaning.

A declared semantic component must match the captured content. Missing blocks or hash mismatches fail the build.

For an unreleased version, capture a new capsule. For a published version, use the capsule created from that exact release.

Handle old releases

Legacy history entries without semantic data use syntax-only rendering.

Once a release declares semantic data, FsLiveDocs does not silently fall back to syntax-only output.