feat: add task status transition utility

[helseaCat]

Description

Add a task status transition utility that defines the valid state machine for task workflows (TODO → IN_PROGRESS → IN_REVIEW → DONE). This will be consumed by the TaskDetailPage to render valid transition buttons.

Changes

• Add src/utils/transitions.ts with getValidTransitions, isValidTransition, and STATUS_LABELS

Testing done

• No new warnings
• Self-reviewed

Checklist

• No new warnings
• Self-reviewed

Summary by CodeRabbit

• New Features
  • Added consistent, validated task status transitions across the workflow (TODO → In Progress → In Review → Done).
  • Improved task status presentation with human-readable labels for each status.
• Bug Fixes
  • Prevents invalid status changes to ensure task state progression follows the defined workflow.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: bc3e34ce-b7ec-4bce-af8e-e698aa7c80df

📥 Commits

Reviewing files that changed from the base of the PR and between cbdba20 and 9c25db2.

📒 Files selected for processing (1)

• nexus-frontend/src/utils/transitions.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• nexus-frontend/src/utils/transitions.ts

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📝 Walkthrough

Walkthrough

A new utility file nexus-frontend/src/utils/transitions.ts is added. It defines an internal TRANSITION_MAP encoding a linear TODO → IN_PROGRESS → IN_REVIEW → DONE state machine, and exports getValidTransitions, isValidTransition, and STATUS_LABELS.

Changes

Task Status Transition Utility

Layer / File(s)	Summary
State machine, transition helpers, and status labels nexus-frontend/src/utils/transitions.ts	Adds TRANSITION_MAP encoding the linear task status flow with terminal empty arrays, exports getValidTransitions to look up allowed next statuses, isValidTransition to validate a specific status move, and STATUS_LABELS mapping each TaskStatus to a human-readable string.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐇 A map of tasks laid end to end,
From TODO on to DONE we wend,
Each hop and skip a lawful leap,
No status lost, no promise cheap.
The rabbit checks each label right —
Transitions tidy, clean, and bright! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely summarizes the main change: introducing a new task status transition utility. It is specific, clear, and directly reflects the primary objective of the pull request.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/task-status-transitions

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[coderabbitai]

🧹 Nitpick comments (1)

nexus-frontend/src/utils/transitions.ts (1)

7-12: ⚡ Quick win

Avoid exposing mutable transition arrays from the internal state map.

getValidTransitions currently returns the same array instance stored in TRANSITION_MAP. A caller can mutate it (push, splice) and silently change global transition rules at runtime.

Proposed hardening change

-const TRANSITION_MAP: Record<TaskStatus, TaskStatus[]> = {
+const TRANSITION_MAP: Readonly<Record<TaskStatus, readonly TaskStatus[]>> = {
   TODO: ['IN_PROGRESS'],
   IN_PROGRESS: ['IN_REVIEW'],
   IN_REVIEW: ['DONE'],
   DONE: [],
 };
@@
 export function getValidTransitions(currentStatus: TaskStatus): TaskStatus[] {
-  return TRANSITION_MAP[currentStatus] ?? [];
+  return [...(TRANSITION_MAP[currentStatus] ?? [])];
 }

Also applies to: 18-20

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@nexus-frontend/src/utils/transitions.ts` around lines 7 - 12, The
getValidTransitions function returns direct array references from the
TRANSITION_MAP constant, allowing callers to mutate these arrays and
inadvertently modify global transition rules. Instead of returning the array
reference directly from TRANSITION_MAP, create and return a shallow copy of the
array (using spread operator or slice method) to prevent external mutations from
affecting the internal state.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@nexus-frontend/src/utils/transitions.ts`:
- Around line 7-12: The getValidTransitions function returns direct array
references from the TRANSITION_MAP constant, allowing callers to mutate these
arrays and inadvertently modify global transition rules. Instead of returning
the array reference directly from TRANSITION_MAP, create and return a shallow
copy of the array (using spread operator or slice method) to prevent external
mutations from affecting the internal state.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 91f00d55-5624-4a5b-a4ad-6b4318718039

📥 Commits

Reviewing files that changed from the base of the PR and between 0f0e196 and cbdba20.

📒 Files selected for processing (1)

• nexus-frontend/src/utils/transitions.ts