Change events.out to pool amounts instead of fluxes

[Alomir]

Summary

• What: Change values in events.out to pool amounts instead of flux values
• Motivation: Reduce confusion when reading events.out

How was this change tested?

Other than values in events.out, there should be no functional changes in this PR.

• All existing unit tests pass (after update for testEventOutputFile canned output)
• smoke tests pass for sipnet.out

Updated events.out for relevant smoke tests are included. Since there were no changes in sipnet.out for the smoke tests, there is no output capture for smoke-check.py.

Related issues

• Fixes Change flux values to pool amounts in events.out #348

Checklist

• Related issues are listed above. PRs without an approved, related issue may not get reviewed.
• PR title has the issue number in it ("[#] <concise description of proposed change>")
• Tests added/updated for new features (if applicable)
• Documentation updated (if applicable)
• docs/CHANGELOG.md updated with noteworthy changes
• Code formatted with clang-format (run git clang-format if needed)

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Note: See CONTRIBUTING.md for additional guidance. This repository uses automated formatting checks; if the pre-commit hook blocks your commit, run git clang-format to format staged changes.

[Copilot]

Pull request overview

Updates SIPNET’s events.out output to report per-event pool deltas (amounts applied over the timestep) instead of per-day flux rates, to reduce confusion when interpreting event diagnostics.

Changes:

• Switch event writing in processEvents() (and leaf-on computed output) from fluxes.* rate-style values to timestep deltas and remove the fluxes. prefix from parameter names.
• Update unit-test canned outputs and smoke-test events.out baselines to match the new event output semantics.
• Refresh user-facing documentation and changelog to describe the new events.out format.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/smoke/russell_3/events.out	Updates smoke baseline to new events.out pool-delta values and parameter names.
tests/smoke/russell_2/events.out	Updates smoke baseline to new events.out pool-delta values and parameter names (includes fert events).
tests/smoke/russell_1/events.out	Updates smoke baseline to new events.out pool-delta values and parameter names.
tests/sipnet/test_events_infrastructure/events_output_no_header.out	Updates unit-test expected output for no-header event output format/values.
tests/sipnet/test_events_infrastructure/events_output_header.out	Updates unit-test expected output for header-included event output format/values.
src/sipnet/sipnet.c	Writes leaf-on computed event values as timestep deltas and drops fluxes. prefix for those fields.
src/sipnet/events.c	Writes scheduled/instant event outputs as timestep deltas with event* parameter names (while still accumulating per-day event fluxes internally).
docs/user-guide/model-outputs.md	Updates the events.out example and description to reflect pool-delta outputs and new parameter names.
docs/CHANGELOG.md	Notes the user-visible change in events.out semantics.

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[Alomir]

When you're right, you're right. Will fix.

[dlebauer]

LGTM, though holding off on approval until the copilot feedback is addressed