docs: phase out prominent http/https specifier examples

[bartlomieju]

Summary

• Remove most HTTP/HTTPS URL import examples across runtime docs, replacing them with jsr: and npm: specifiers
• Condense the "HTTPS imports" section in modules.md to a single brief reference with a caution note
• Remove the "Overriding HTTPS imports" subsection entirely
• Update code examples in CLI docs, JSX, TypeScript config, and migration guide to use local files or npm: specifiers

Test plan

• Verify no broken internal links from removed sections
• Confirm the remaining HTTPS imports section in modules.md reads well as a standalone reference
• Check that JSX pragma example with import map note is clear

🤖 Generated with Claude Code

[fibibot]

runtime/reference/ts_config_migration.md line 397 now shows /// <reference types="./types.d.ts" /> — identical to the example three lines above. The prose between them still reads "It can be a fully qualified URL as well:", so the second code block needs to actually be a URL (swap the deno.land/x example for an npm: or https://esm.sh/... one), or the surrounding sentence needs to be rewritten. As-is the page contradicts itself.

• nit: runtime/fundamentals/modules.md:323 keeps https://deno.land/x/oak/mod.ts as the canonical HTTPS-imports example, but elsewhere this repo recommends jsr:@oak/oak. A neutral CDN example would avoid the mixed signal.
• nit: runtime/reference/ts_config_migration.md:487-490 still describes esm.sh's X-TypeScript-Types header but now closes with "for most use cases, npm: specifiers are the recommended way" — fine, but no npm: example is shown for the type-resolution case it was illustrating.

[lunadogbot]

One blocker remains:

1. /// <reference types="./types.d.ts" /> on line 397 contradicts the sentence immediately above it: the text says this example can be a fully qualified URL, but it now repeats the same relative-path example from line 389. Please restore a URL example or rewrite the sentence so the duplicate block is intentional.

• nit: https://deno.land/x/oak/mod.ts is still the canonical HTTPS import in runtime/fundamentals/modules.md; a neutral URL would avoid the mixed signal after this PR removes deno.land/x elsewhere.