[Docs] Integrate 26.06 documentation PRs and stage the version train

[lbliii]

Parent tracker: #2118

Goal

Integrate the 26.06 documentation PR set without losing content at cross-PR merge boundaries, then stage the version train for publication.

Why this is required

An adversarial combined-tree merge found four real content-conflict groups even though the individual PRs pass validation:

• [codex] docs: add audio tagging pipeline guide #2135 and [codex] docs: add long-form audio cutting guide #2136 both add cards to the audio overview and tutorial index.
• [codex] docs: document native pipeline resumability #2134 and [codex] Document stage worker sizing and backend overrides #2142 both extend the ProcessingStage API reference.
• [codex] docs: clarify deduplication input discovery #2130 and [codex] Document memory-efficient semantic dedup fitting #2149 both extend the semantic deduplication page at the same insertion point.
• [codex] publish 26.06 release notes and migration checklist #2143 and [codex] Rewrite InferenceServer docs for Ray Serve and Dynamo #2147 both update the release-notes page. [codex] publish 26.06 release notes and migration checklist #2143 is the canonical 26.06 rollup and must preserve the typed InferenceServer/Dynamo material.

Timing

Release blocker. Perform the reconciliation after the detailed feature PRs merge, but before #2143 merges and before any docs/v1.3.0 publication tag is pushed.

Acceptance criteria

• Merge or rebase the audio pair and preserve both tutorial cards on both landing pages.
• Merge or rebase the resumability/worker-sizing pair and preserve both task-lineage and backend-configuration sections.
• Merge or rebase the deduplication pair and preserve both input-discovery and K-means fitting guidance.
• Merge [codex] Rewrite InferenceServer docs for Ray Serve and Dynamo #2147 before [codex] publish 26.06 release notes and migration checklist #2143, then rebase [codex] publish 26.06 release notes and migration checklist #2143 and preserve the complete 26.06 release narrative.
• Run fern check, git diff --check, and the generated-reference broken-link job against the combined tree.
• Stage v26.06, update fern/docs.yml, redirects, and the latest.yml symlink according to the version ship checklist.
• Do not push the production docs/v* tag until release authorization is explicit.