fix(backchecks): apply the duplicate option and target % from settings

[iabaako]

Pull Request Summary 🚀

What does this PR do? 📝

Makes the backcheck duplicate-handling option and target % chosen in the settings panel actually take effect. Closes #299.

 backchecks_report_settings
   return BackcheckSettings(
-    backcheck_goal=...,            # not a model field → silently dropped
-    drop_duplicates=...,           # not a model field → silently dropped
+    backcheck_target_percent=...,
+    drop_duplicates_option=...,    # read by compute_backcheck_analysis
   )

 _render_tracking_options
-  save_check_settings(..., {"backcheck_goal": ...})            # never reloaded
+  save_check_settings(..., {"backcheck_target_percent": ...})  # reloads next session

Why is this change needed? 🤔

BackcheckSettings ignores unknown keywords, so both values fell back to their defaults:

• Duplicate IDs were always dropped, whatever the user selected.
• The target was always 10, whatever the input said.

How was this implemented? 🛠️

• Pass the model's field names in backchecks_report_settings.
• Save the target under backcheck_target_percent so load_default_backchecks_settings reloads it. Targets saved under the old backcheck_goal key were never applied and are now ignored (noted in the CHANGELOG).
• Rename the backcheck_goal local to backcheck_target_percent so it matches the field it feeds.

Not done: extra="forbid" on BackcheckSettings (suggested in the issue). The model is also built from dicts that legitimately carry extra keys, so forbid would raise errors:

• the saved backchecks-tab settings (string_case_option, enum_bcer_stats_view, …) merged in load_default_backchecks_settings
• backchecker_team from output_view_template.py, passed to BackcheckSettings(**config) in report_ui.py

Follow-ups found during review (out of scope, planned in #318):

#318 (7 of 13 in the stack, after #300) redesigns the backcheck target metrics and covers all three:

• Nothing in checks/backchecks/ reads backcheck_target_percent. The value now arrives correctly but still has no visible effect. Backchecks: track progress against the backcheck target #318 adds on-track coverage against the target and progress towards the expected total.
• The input is labelled "Target number of backchecks", but the field is a percentage. Backchecks: track progress against the backcheck target #318 relabels it "Backcheck target (%)", limited to 0–100.
• A bug that was already there: backcheck_target_percent=None from the page config raises a ValidationError when BackcheckSettings(**config) builds the settings (the model field is a plain int). Backchecks: track progress against the backcheck target #318 makes the field accept "not set" and falls back to 10% with a warning.

How to test or reproduce ? 🧪

uv run python -m pytest tests/checks/backchecks/test_settings_ui.py
just test

New tests in tests/checks/backchecks/test_settings_ui.py:

Test	Before	After
test_report_settings_keeps_selected_duplicate_option	❌ 'drop' == 'last'	✅
test_report_settings_keeps_selected_target_percent	❌ 10 == 35	✅
test_render_tracking_options_saves_under_model_field_name	❌ saved {'backcheck_goal': 35}	✅

Full suite: 3511 passed, 6 skipped. Existing test_compute.py tests already cover how first / last / drop change the results.

Manual: in a backchecks page, choose Keep Last Entry and set a non-default target. Duplicates are now kept rather than dropped, and the target persists after a reload.

Merge risk: low and easy to undo (revert the commits). It affects only the backcheck report: projects whose saved settings say first or last will now keep duplicate IDs instead of dropping them, which changes the backcheck counts users see.

Screenshots (if applicable) 📷

N/A. The settings panel looks the same; only the values passed through it change.

Checklist ✅

• I have run and tested my changes locally
• I have limit this PR to less than 1000 lines of code change (if not, explain why)
• I have updated/added tests to cover my changes (if applicable)
• I have updated/added requirements to cover my changes (if applicable): N/A, no new dependencies
• I have run linting and formatting on any code changes (if applicable)
• I have updated the documentation (README, etc.) accordingly: CHANGELOG entry under Fixed
• I have reviewed and resolved any merge conflict

Reviewer Emoji Legend

	:code:	Meaning
😃👍💯	:smiley: :+1: :100:	I like this... ...and I want the author to know it! This is a way to highlight positive parts of a code review.
⭐⭐⭐	:star: :star: :star:	Important to fix before PR can be approved... And I am providing reasons why it needs to be addressed as well as suggested improvements.
⭐⭐	:star: :star:	Important to fix but non-blocking for PR approval... And I am providing suggestions where it could be improved either in this PR or later.
⭐	:star:	Give this some thought but non-blocking for PR approval... ...and consider this a suggestion, not a requirement.
❓	:question:	I have a question. This should be a fully formed question with sufficient information and context that requires a response.
📝	:memo:	This is an explanatory note, fun fact, or relevant commentary that does not require any action.
⛏	:pick:	This is a nitpick. This does not require any changes and is often better left unsaid. This may include stylistic, formatting, or organization suggestions and should likely be prevented/enforced by linting if they really matter
♻️	:recycle:	Suggestion for refactoring. Should include enough context to be actionable and not be considered a nitpick.

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟡 Changes recommended

The target cannot persist because its save callback still activates the old session-state key.

Review effort: Balanced
Findings: 1

Open (1)

• Fix mismatched session-state key blocking target persistence · New

What changed in this PR

Fixes backcheck settings field mapping so duplicate handling and target percentages reach BackcheckSettings.

Changes:

• Uses the correct model field names.
• Persists the target under its model field name.
• Adds regression tests and changelog documentation.

File	Description
src/​datasure/​checks/​backchecks/​settings_ui.py	Corrects settings mapping and persistence key.
tests/​checks/​backchecks/​test_settings_ui.py	Tests non-default setting propagation.
CHANGELOG.md	Documents the fix.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud