docs(recipes): restore duration_seconds + version pin sweep

[zuchka]

Summary

Item 3 of 4 in the inward-polish roadmap. Pure docs sweep across docs/recipes/ (no code).

• Restores {{ .duration_seconds }} to every run.exit message template (8 platform recipes + _template.md). Engine support landed in v0.10.0 (commit 5fda9c1) but no recipe had been re-adopted since the feature was stripped from mlflow in fcdc11e.
• Normalizes DING binary pin to >= v0.10.0 across all 9 files (was a range of v0.3.0–v0.8.0).
• Bumps container image tag (ghcr.io/ding-labs/ding:v0.7.0 → :v0.10.0) in argo + k8s recipes (3 occurrences each).
• Adjacent consistency: drain_timeout deep-link in 5 recipes (gitlab-ci, jenkins, buildkite, mlflow, ray), "full notifier reference" phrasing in modal + ray Configuration sections, internal/ingester/json.go leak removed from modal.
• mlflow/modal/ray's "What you get" rendered exit-alert excerpts updated to match the YAML (illustrative durations: 42s / 287s / 1843s).

mode: end-of-run sweep already shipped in 9cca220; no changes there.

The 3 "for the full reference" instances in gitlab-ci, buildkite, kubernetes-jobs that link to a specific notifier type are deliberately left as-is — different sentence pattern.

Test plan

• grep -L ">= v0.10.0" docs/recipes/*.md — empty (all pinned)
• grep -L "duration_seconds" docs/recipes/*.md — empty (all reference it)
• Anchor sweep across recipes — 11 internal .md#anchor refs all resolve
• ding validate --config on extracted buildkite + mlflow YAML — both exit 0
• ding test-rule end-to-end render: synthetic run.exit event with duration_seconds=42.5 renders (exit 1 after 42.5s) (not <no value>)
• Visual diff review — 33 ins / 33 del, no whitespace drift, no unintended edits

Out of scope (deliberately)

• mode: end-of-run sweep (already shipped in 9cca220)
• Recipe section restructuring
• index.md status changes

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