feat(effort): five shifter skills, lib/effort-shift.md, model-gate second axis

skills/effort-high/SKILL.md

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+---
+name: effort-high
+description: Investigation shift. Deeper reasoning for diagnosis, LOCATE, contract drafting, refactor judgement inside feat, hotfix and bugfix runs.
+effort: high
+---
+Effort shifted to high for the rest of this turn (lib/effort-shift.md). Continue with the caller's next step.

skills/effort-low/SKILL.md

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+---
+name: effort-low
+description: Bookkeeping shift. Lowers reasoning to the cheapest level for the rest of the turn: journal lines, memory commits, capitalize, release bookkeeping, status output.
+effort: low
+---
+Effort shifted to low for the rest of this turn (lib/effort-shift.md). Continue with the caller's next step.

skills/effort-max/SKILL.md

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+---
+name: effort-max
+description: Escalation shift. Maximum reasoning when a verify or security loop hits its cap, a gate fails twice, or error recovery starts in ship-feature.
+effort: max
+---
+Effort shifted to max for the rest of this turn (lib/effort-shift.md). Continue with the caller's next step.

skills/effort-medium/SKILL.md

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+---
+name: effort-medium
+description: Orchestration shift. Standard reasoning between two dispatches: read a subagent report, pick the next step, relay a gate verdict, route a branch.
+effort: medium
+---
+Effort shifted to medium for the rest of this turn (lib/effort-shift.md). Continue with the caller's next step.

skills/effort-xhigh/SKILL.md

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+---
+name: effort-xhigh
+description: Reflection shift. Deep reasoning for brainstorm, planning, challenge synthesis and audit verdicts before a human validation gate.
+effort: xhigh
+---
+Effort shifted to xhigh for the rest of this turn (lib/effort-shift.md). Continue with the caller's next step.