docs: drop the inverted draft setup (#948)

[ocots]

Closes #948.

Before

docs/make.jl: draft = true global, and 43 content pages each carrying

```@meta
Draft = false

to opt back into `@example` / `@repl` execution — a double negative across 44 files. The
guided tour additionally got `Draft = false` injected by a Literate `postprocess`.

- A new page without the marker is silently **not executed**.
- No fast `draft = true` pass possible (nav / link / `@ref` / `@extref` / render checks)
  without stripping 43 markers first.

## After

- `make.jl`: `draft = false` default — every page executes (what a published build does).
  Flip the one flag locally for a fast build.
- 43 `@meta Draft = false` blocks removed; guided-tour injection removed.
- `make.jl` comments refreshed; stale `:example_block` note trimmed (CTParser#341 closed).
- Opt a single page **out** of execution with `Draft = true` in its `@meta`.

Safe: only `api/ecosystem.md` (no code) and generated `guided-tour.md` lacked a marker;
neither relied on being skipped.

## Verification

Full local build, `julia --project=. docs/make.jl` (`draft = false`):

- exit 0; `Doctest`, `ExpandTemplates`, `ExtCrossReferences`, `CrossReferences`,
  `CheckDocument`, `RenderDocument` all pass
- every `@example` / `@repl` executes — inline SVG figures present in `results/plot.html`,
  `getting-started/guided-tour.html`, …; computed values rendered in
  `getting-started/first-problem.html`
- `@extref` unresolved: **0**; `@ref` unresolved: **0**
- only residual warnings: 2× "Failed to load inventory CTDirect/CTParser" (local
  `objects.inv` absent → network fallback), deploy-env, favicon — all pre-existing

`docs/src/assets/Manifest.toml` deliberately **not** touched here — no dep/compat change;
the CTModels 0.19.4-beta / CTBase 0.30.4-beta Manifest refresh belongs in its own PR.

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