[ALICE3] fix linter and code-check for fasttracker

[jesgum]

No description provided.

[github-actions]

O2 linter results: ❌ 40 errors, ⚠️ 27 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/code-check for 3b66bc4 at 2026-09-11 18:05:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 1 errors and 68 warnings.'
Found 1 errors and 68 warnings.
++ [[ 1 -gt 0 ]]
++ cat /sw/BUILD/4db667a8acd8d8bf02cbe0ee265b0b015528ad81/O2Physics-code-check/errors.txt
ALICE3/Core/FastTracker.cxx:43:1: error: included header RtypesCore.h is not used directly [misc-include-cleaner,-warnings-as-errors]
++ [[ 68 -gt 0 ]]
++ cat /sw/BUILD/4db667a8acd8d8bf02cbe0ee265b0b015528ad81/O2Physics-code-check/warnings.txt
ALICE3/Core/FastTracker.cxx:53:1: warning: nested namespaces can be concatenated [modernize-concat-nested-namespaces]
ALICE3/Core/FastTracker.cxx:127:9: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
ALICE3/Core/FastTracker.cxx:128:9: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
ALICE3/Core/FastTracker.cxx:129:9: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
ALICE3/Core/FastTracker.cxx:189:39: warning: use starts_with instead of rfind [modernize-use-starts-ends-with]
ALICE3/Core/FastTracker.cxx:195:9: warning: use auto when initializing with a template cast to avoid duplicating the type name [modernize-use-auto]
ALICE3/Core/FastTracker.cxx:204:9: warning: use auto when initializing with a cast to avoid duplicating the type name [modernize-use-auto]
ALICE3/Core/FastTracker.cxx:204:21: warning: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
ALICE3/Core/FastTracker.cxx:258:54: warning: statement should be inside braces [readability-braces-around-statements]
ALICE3/Core/FastTracker.cxx:305:9: warning: variable 'sx' is not initialized [cppcoreguidelines-init-variables]
ALICE3/Core/FastTracker.cxx:305:13: warning: variable 'goodHit' is not initialized [cppcoreguidelines-init-variables]
ALICE3/Core/FastTracker.cxx:315:16: warning: narrowing conversion from 'float' to 'int' [bugprone-narrowing-conversions]
ALICE3/Core/FastTracker.cxx:320:3: warning: uninitialized record type: 'posIni' [cppcoreguidelines-pro-type-member-init]
ALICE3/Core/FastTracker.cxx:382:33: warning: implicit conversion 'int' -> 'bool' [readability-implicit-bool-conversion]
ALICE3/Core/FastTracker.cxx:384:17: warning: statement should be inside braces [readability-braces-around-statements]
ALICE3/Core/FastTracker.cxx:397:9: warning: do not use 'else' after 'return' [readability-else-after-return]
ALICE3/Core/FastTracker.cxx:440:41: warning: implicit conversion 'int' -> 'bool' [readability-implicit-bool-conversion]
ALICE3/Core/FastTracker.cxx:456:35: warning: statement should be inside braces [readability-braces-around-statements]
ALICE3/Core/FastTracker.cxx:468:5: warning: uninitialized record type: 'spacePoint' [cppcoreguidelines-pro-type-member-init]
ALICE3/Core/FastTracker.cxx:474:5: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
ALICE3/Core/FastTracker.cxx:484:72: warning: redundant explicit casting to the same type 'float' as the sub-expression, remove this casting [readability-redundant-casting]
ALICE3/Core/FastTracker.cxx:484:101: warning: redundant explicit casting to the same type 'float' as the sub-expression, remove this casting [readability-redundant-casting]
ALICE3/Core/FastTracker.cxx:500:33: warning: implicit conversion 'int' -> 'bool' [readability-implicit-bool-conversion]
ALICE3/Core/FastTracker.cxx:570:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
ALICE3/Core/FastTracker.cxx:598:20: warning: do not use reinterpret_cast [cppcoreguidelines-pro-type-reinterpret-cast]
ALICE3/Core/FastTracker.cxx:624:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
ALICE3/Core/FastTracker.h:36:1: warning: nested namespaces can be concatenated [modernize-concat-nested-namespaces]
ALICE3/Core/FastTracker.h:52:11: warning: use '= default' to define a trivial destructor [modernize-use-equals-default]
ALICE3/Core/FastTracker.h:62:3: warning: function 'getLayer' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:63:3: warning: function 'getLayers' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:64:3: warning: function 'getLayerIndex' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:65:3: warning: function 'getNLayers' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:66:3: warning: function 'isLayerInert' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:129:3: warning: function 'getNIntercepts' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:130:3: warning: function 'getNSiliconPoints' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:131:3: warning: function 'getNGasPoints' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:132:3: warning: function 'getGoodHitProb' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:136:3: warning: function 'getNHits' should be marked [[nodiscard]] [modernize-use-nodiscard]
ALICE3/Core/FastTracker.h:137:3: warning: function 'getHitX' should be marked [[nodiscard]] [modernize-use-nodiscard]
[0 more errors; see full log]

Full log here.