chore(task-utils): promote inline plugin-settings-lib.sh to shared-lib plugin

[jack-nsheaps]

Summary

R2 of the task-utils redesign added hooks/plugin-settings-lib.sh — a 3-tier (env → project settings.yaml → plugin defaults) yq-backed config reader — inline in the task-utils plugin. The reason it was inlined rather than sourced from ai-mktpl's shared-lib plugin is that the nsheaps/agents repo does not currently have a mechanism to depend on ai-mktpl plugins.

Once that dependency story exists, the inline copy should be removed and the canonical implementation should live in shared-lib. Until then, task-utils carries a duplicate.

Requirements

• Confirm the agents repo has a sanctioned way to depend on ai-mktpl plugins (separate prerequisite — track elsewhere if it doesn't exist yet).
• Move the canonical implementation of the 3-tier config reader to shared-lib in ai-mktpl (if not already there) and bump shared-lib version.
• Update task-utils to source the shared-lib version (replace inline hooks/plugin-settings-lib.sh body with a sourceable shim or delete it entirely).
• Update all callers in task-utils hooks (require-task-in-progress.sh, task-native-warning.sh, task-sync-from-legacy.sh, etc.) to use the shared-lib path.
• Bump task-utils version (likely 0.2.x patch since it's an internal refactor).
• Update task-utils tests to reflect the new source path.

Source

Identified during R2 of the redesign. Handler decision in report §"Handler Decisions Applied" item 2: "Config mechanism: plugins.settings.yaml 3-tier with inline yq-backed plugin-settings-lib.sh — done (not shared-lib, as agents repo cannot depend on ai-mktpl)."

Related

• Blocked by: fix(ci): auto-version-bump workflow false-positive when version already manually bumped #169 (CI must be clean before more task-utils PRs land)
• Originating PR: nsheaps/agents#157 — introduced the inline lib

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Issue created by Jack Oat (AI agent) on behalf of nsheaps.