docs: converge on one product name and link the table of contents

[jsugg]

Four names

Surface	Was
README.md:5,14	Alt-Text 4 All
package.json / repo / Postman collection	alt-text-generator
docs/openapi.base.json, config/swagger-base.js:24	AI-Powered Alternative Text Provider API
Render OPENROUTER_TITLE (live)	Alt Text 4 All (no hyphen)

Plus two competing descriptions. The OpenAPI title is the public-facing one —
config/swagger.js serves that artifact verbatim to swagger-ui and downstream
codegen — so which spelling won was not a cosmetic question.

Now

Alt-Text 4 All, everywhere it is a product name:

README.md:5                 Alt-Text 4 All              (already correct)
package.json description    Alt-Text 4 All — ...
config/swagger-base.js      Alt-Text 4 All
docs/openapi.base.json      Alt-Text 4 All              (regenerated)
Postman collection          Alt-Text 4 All API Contract Harness
Render OPENROUTER_TITLE     Alt-Text 4 All              [live, done]

package.json name stays alt-text-generator — npm names cannot contain
spaces or capitals, and it is the package identifier, not the product name. The
repo, the Render service, and the collection filename keep it for the same
reason. That is a deliberate distinction, not an oversight.

The single description is lifted from the README's own overview line rather than
invented, so the package, the API, and the docs repeat wording a reader has
already seen instead of offering a third variant.

docs/openapi.base.json is generated, not edited

Regenerated via npm run openapi:generate from swagger-base.js:

openapi:validate  OK  (8 paths, 8 operations)
openapi:check     OK  matches the generated contract
openapi:diff      OK  backward compatible with origin/main

openapi:diff matters here: title and description are metadata, so no path,
schema, or response moved. Nothing downstream breaks.

Worth noting this PR is the first to exercise #259 in anger — a change touching
docs/openapi.base.json now runs the openapi job instead of skipping it
as a "docs" path.

Table of contents

All 14 entries already matched their ## headings, so this is navigability
only, not a correctness fix. The anchors were generated with the same
slugifyHeading the docs gate uses to validate links — so the gate now checks
its own output, and a heading renamed without updating the TOC fails the docs
check rather than rotting silently.

Verification

docs:validate 8/0 · docs:lint 0 · openapi:validate / check / diff ·
postman:lint (13 folders, 45 requests) · lint · typecheck · 863/863 unit.
The Postman diff is exactly two lines — name and description — with no
reformatting of the 45 requests.