chore: improve logging

[zepfred]

The PR adds additional logging information at the DEBUG level:

11:05:45.487 DEBUG [pool-5-thread-1] Custom phase (1) started.
11:05:45.488 DEBUG [pool-5-thread-1]     Custom step (0), time spent (19), score (0hard/-38007850000medium/-29758913soft),     best score (0hard/-38007850000medium/-29758913soft).
11:05:45.491  INFO [pool-5-thread-1] Custom phase (1) ended: time spent (22), best score (0hard/-38007850000medium/-29758913soft), move evaluation speed (0/sec), step total (1).

11:05:45.497 DEBUG [pool-5-thread-1] Multi-Threaded Construction Heuristic Decider started, move threads (4)
11:05:45.497 DEBUG [pool-5-thread-1] Construction Heuristic phase (2) started.
11:05:45.512 DEBUG [pool-5-thread-1]     CH step (0), time spent (43), score (0hard/-37007850000medium/-29479796soft), selected move count (2), picked move (SolverVisit{id=5f093b6c, visitGroup=null} {null -> SolverVehicleShift{id=4ba8b9dc}[0]}).
...
11:05:45.628 DEBUG [pool-5-thread-1]     CH step (158), time spent (159), score (0hard/-30000medium/-4204205soft), selected move count (18), picked move (ai.timefold.solver.core.impl.heuristic.move.SelectorBasedNoChangeMove@41d4d9d7).
11:05:45.636 DEBUG [pool-5-thread-1] Multi-Threaded Construction Heuristic Decider ended
11:05:45.636  INFO [pool-5-thread-1] Construction Heuristic phase (2) ended: time spent (167), best score (0hard/-30000medium/-4204205soft), effective move evaluation speed (15209/sec), step total (159).

11:05:45.649 DEBUG [pool-5-thread-1] Distance Matrix building ended, origin size (158), maximum destination size (40).
11:05:45.653 DEBUG [pool-5-thread-1] Distance Matrix building ended, origin size (158), maximum destination size (40).
11:05:45.657 DEBUG [pool-5-thread-1] Distance Matrix building ended, origin size (158), maximum destination size (40).
11:05:45.657 DEBUG [pool-5-thread-1] Multi-Threaded Local Search Decider started, move threads (4)
11:05:45.657 DEBUG [pool-5-thread-1] Local Search phase (3) started.
11:05:45.684 DEBUG [pool-5-thread-1]     LS step (0), time spent (215), score (0hard/-30000medium/-4203148soft), new best score (0hard/-30000medium/-4203148soft), accepted/selected move count (1/38), picked move (SolverVisit{id=797fb983, visitGroup=null} {SolverVehicleShift{id=9419b027}[0]} <-> SolverVisit{id=b20ce24e, visitGroup=null} {SolverVehicleShift{id=0ed0fa07}[0]}).
...
11:06:29.208 DEBUG [pool-5-thread-1]     LS step (130677), time spent (43739), score (0hard/0medium/-3929089soft),     best score (0hard/0medium/-3929083soft), terminated prematurely after selecting 98 moves.
11:06:29.211 DEBUG [pool-5-thread-1] Multi-Threaded Local Search Decider ended
11:06:29.211  INFO [pool-5-thread-1] Local Search phase (3) ended: time spent (43742), best score (0hard/0medium/-3929083soft), effective move evaluation speed (117863/sec), step total (130678).

[Copilot]

Pull request overview

This PR adds new DEBUG-level “phase started” log lines across several solver phases to make solver lifecycle logs more complete and easier to correlate with existing step/phase-end logging.

Changes:

• Log “Custom phase started” at DEBUG when a custom phase begins.
• Log “Construction Heuristic phase started” at DEBUG when CH begins.
• Log “Exhaustive Search phase started” and “Local Search phase started” at DEBUG when those phases begin.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
core/src/main/java/ai/timefold/solver/core/impl/phase/custom/DefaultCustomPhase.java	Adds a DEBUG log line at custom phase start.
core/src/main/java/ai/timefold/solver/core/impl/constructionheuristic/DefaultConstructionHeuristicPhase.java	Adds a DEBUG log line at construction heuristic phase start.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/DefaultExhaustiveSearchPhase.java	Adds a DEBUG log line at exhaustive search phase start.
core/src/main/java/ai/timefold/solver/core/impl/localsearch/DefaultLocalSearchPhase.java	Adds a DEBUG log line at local search phase start.

[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

[triceo]

From the provided log, you can see that this brings zero benefit.
The delay - where there is a delay - is not wrapped by any logging statement; therefore this logging is pointless.

IMO we can just close this.