fix: handle condition waiting better in thread_task_executor

[no23reason]

The pattern used for the condition waiting was not robust enough and was susceptible to a race condition.

This prevents that class of race condition by persisting the status and checking it when the signal is received, rather than relying on the assumption the notification always happens after all the relevant waiters are ready to receive it.

Also, do the finalizer retrieval outside of the critical section: if it fails, it no longer holds the lock forever.

JIRA: CQ-2677
risk: low

Summary by CodeRabbit

• Bug Fixes
  • Improved task completion tracking to ensure completion waits return reliably and avoid unnecessary delays.
  • Improved cleanup handling for data retrieval tasks, helping resources be released consistently when processing finishes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: f02b18b7-7e82-4dd4-a88d-221730aa8640

📥 Commits

Reviewing files that changed from the base of the PR and between 0b272b4 and 818cdff.

📒 Files selected for processing (2)

• packages/gooddata-flight-server/src/gooddata_flight_server/server/flight_rpc/server_methods.py
• packages/gooddata-flight-server/src/gooddata_flight_server/tasks/thread_task_executor.py

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📝 Walkthrough

Walkthrough

The change adds explicit completion-state tracking to _TaskExecution waits and initializes task-result finalizer middleware before acquiring task data, while preserving callback registration and lock-release behavior.

Changes

Task result lifecycle

Layer / File(s)	Summary
Explicit task completion predicate packages/gooddata-flight-server/src/gooddata_flight_server/tasks/thread_task_executor.py	_TaskExecution tracks _done, sets it when result processing completes, and waits for the flag before returning or timing out.
Earlier finalizer initialization packages/gooddata-flight-server/src/gooddata_flight_server/server/flight_rpc/server_methods.py	do_get_task_result creates finalizer middleware before acquiring task data and retains end-callback registration.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: hkad98, lupko, pcerny

Poem

A rabbit waits beneath the moon,
For tasks to finish, safely soon.
A flag says “done,” the locks unwind,
The finalizer starts in time.
Hop, hop—clean flows align!

🚥 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 is concise and accurately reflects the main thread_task_executor condition-waiting fix.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 78.02%. Comparing base (0b272b4) to head (818cdff).

Files with missing lines	Patch %	Lines
..._flight_server/server/flight_rpc/server_methods.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1690   +/-   ##
=======================================
  Coverage   78.02%   78.02%           
=======================================
  Files         271      271           
  Lines       18637    18639    +2     
=======================================
+ Hits        14542    14544    +2     
  Misses       4095     4095           

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