[P2 docs] Fix generated AB4100 diagnostics reference to include Amp as a built-in target

[ScriptedAlchemy]

Drift found during #754 capability audit

Main 14c9822bc6c01d8ff2788454d0e1dc7861bc3816 has Amp in the production default registry, but docs/diagnostics.md still says AB4100's built-in registry publishes only claude, codex, cursor, and portable, and its recovery text lists only those four.

The Rspress reference/diagnostics.md page is generated from this repository contract, so the stale source propagates into the public docsite even though reference/configuration.mdx, targets-artifacts.mdx, and #754's capability guide correctly list all five targets.

Required correction

• Add amp to AB4100's built-in-target statement and recovery list.
• Search docs/diagnostics.md for other exhaustive built-in-target enumerations that predate Amp and correct only current contract prose; do not rewrite historical changesets.
• Regenerate/verify both locale diagnostics pages through the normal docsite generation path rather than hand-editing generated website/docs/*/reference/diagnostics.md output.
• Add or retain a guard that compares the documented exhaustive target set with createDefaultRegistry().names() (or another canonical source) so the next built-in adapter cannot silently drift the generated reference.
• Preserve portable as the default and preserve the fact that plugin is not a target.

Acceptance

Built diagnostics reference lists amp, claude, codex, cursor, portable for AB4100 and no current recovery text tells an Amp author that amp is unknown. Run locale/link/docs generation gates. This is documentation-contract drift only; no target or diagnostic behavior change is requested.

[ScriptedAlchemy]

Closed by #758, squash-merged as 0ef0436ef79737485b9f8698d246edc5c6fb115a.

Ask	Where it landed
amp in AB4100's built-in-target statement and recovery list	docs/diagnostics.md AB4100 row: the registry statement and the recovery both read amp, claude, codex, cursor, portable
Other pre-Amp exhaustive enumerations, current prose only	The skill-host lowering preamble; AB3006 (Amp's builtin-tools / mcpServers extension fields and targets.amp); AB3008 (Amp documents no Skill Markdown interpolation engine, so it belongs with Codex, Cursor, portable); AB3009 (foreign-placeholder detection covers Amp documents); AB3010 (Amp is judged by the Agent Skills frontmatter schema plus Amp's own skill MCP rules); the composite-root section; AB4106; AB6023. The stale "unified plugin target's shared document" clauses went with them
Regenerate rather than hand-edit the generated pages	Only docs/diagnostics.md was edited; website/docs/{en,zh}/reference/diagnostics.md is rendered from it at build time, and the built output was read back to confirm both locales list all five targets
A guard against the next silent drift	packages/agent-bundle/tests/diagnostics-doc-targets.test.ts parses AB4100's trigger and recovery target lists out of docs/diagnostics.md and compares both with createDefaultRegistry().names(). Falsified before landing: removing amp from the row fails the test with the target diff
Preserve portable as default and plugin as a non-target	Unchanged

Acceptance: the built diagnostics reference lists amp, claude, codex, cursor, portable
for AB4100 in both locales, and no current recovery text tells an Amp author that amp is
unknown. Gates: pnpm build, pnpm typecheck, pnpm lint, pnpm test:unit (4480 tests, 0
failures), pnpm docs:site:build (locale drift, diagnostics coverage, language parity, 0 broken
links over 30105 anchors).

docs/diagnostics.md's host-scoped config-key list stays at four names deliberately: the Amp
adapter declares no configExtension, so claude, codex, cursor, portable is complete
there, matching reference/configuration.mdx.