feat: Use global [exclude-newer] table instead

[pavelzw]

Description

follow-up of #5786, xref #4545

Discussed with @Hofer-Julian, this is probably a cleaner approach

How Has This Been Tested?

unit tests

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
  • I take responsibility for any AI-generated content in my PR.

Tools: codex

prompt:

i don't like the current exclude-newer approach. let's use the following configuration structure instead:

  [workspace]
  exclude-newer = "7d"
  channels = [{ channel = "my-private-channel", exclude-newer = "0d" }, "conda-forge"]

  [exclude-newer]
  python = "0d"

  [pypi-exclude-newer]
  bolton = "0d"


  ---

  this should be not feature-specific package overrides in `constraints`, `dependencies` and `pypi-dependencies` and pypi dependency-overrides. instead, just a global table.
  dont hesitate to remove unnecessary code. update the tests accordingly

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added sufficient tests to cover my changes.
• I have verified that changes that would impact the JSON schema have been made in schema/model.py.

[pavelzw]

overview of all exclude-newer tests (in 46b7296 (this PR)) by codex

• Here’s the updated overview of exclude-newer test coverage.

  Parsing And Config

  - schema/test_manifest.py:205 validates schema acceptance for workspace exclude-newer, per-channel overrides, [exclude-newer], and [pypi-exclude-newer].
  - crates/pixi_manifest/src/toml/workspace.rs:386 rejects invalid exclude-newer values with a parse error.
  - crates/pixi_manifest/src/toml/channel.rs:182 checks channel-level exclude-newer parsing.
  - crates/pixi_manifest/src/manifests/workspace.rs:3477 parses [exclude-newer] and [pypi-exclude-newer] package tables.
  - crates/pixi_manifest/src/manifests/workspace.rs:3517 verifies package overrides apply.
  - crates/pixi_manifest/src/manifests/workspace.rs:3563 verifies channel overrides apply.
  - crates/pixi_spec/src/exclude_newer.rs:233 now has dedicated unit tests for invalid strings, relative cutoff timing, space-separated timestamps, and serde roundtrips, in addition to the existing
    timestamp/date/duration/display/conversion tests.

  Environment Merge And Precedence

  - crates/pixi_core/src/workspace/environment.rs:807 merges channel-specific cutoffs across multiple features.
  - crates/pixi_core/src/workspace/environment.rs:872 confirms first feature wins for duplicate channel definitions.
  - crates/pixi_core/src/workspace/environment.rs:932 checks precedence: package override > channel override > workspace cutoff.

  Conda Solve And Install

  - crates/pixi/tests/integration_rust/install_tests.rs:1460 verifies a global cutoff pushes the solve from newer foo to older foo.
  - crates/pixi/tests/integration_rust/install_tests.rs:1532 verifies a per-package override re-allows a direct dependency.
  - crates/pixi/tests/integration_rust/install_tests.rs:1578 verifies a per-package override re-allows a transitive/constraint-selected package.

  PyPI Solve

  - crates/pixi/tests/integration_rust/install_tests.rs:1634 is the online integration test for a global PyPI cutoff selecting an older boltons.
  - crates/pixi/tests/integration_rust/pypi_tests.rs:500 verifies [pypi-exclude-newer] can re-allow a package from an explicit per-package index.
  - crates/pixi/tests/integration_rust/pypi_tests.rs:611 verifies the same thing through dependency-overrides.
  - crates/pixi/tests/integration_rust/pypi_tests.rs:784 verifies relative cutoffs reject PyPI candidates without timestamps.

  Build Backend And Pixi-Build

  - crates/pixi_command_dispatcher/tests/integration/main.rs:261 verifies backend/tool env instantiation respects a global cutoff.
  - crates/pixi_command_dispatcher/tests/integration/main.rs:304 verifies backend package-specific overrides can bypass that cutoff for backend resolution.
  - crates/pixi/tests/integration_rust/build_tests.rs:549 verifies source build environments inherit exclude-newer for build dependencies.
  - crates/pixi/tests/integration_rust/build_tests.rs:632 now verifies pixi-build package overrides clear build and host dependency exclusions, leaving only the timestamp-less source package as the
    remaining blocker.

  Lockfile Satisfiability

  - crates/pixi_core/src/lock_file/satisfiability/mod.rs:2814 runs the failing fixture suite.
  - tests/data/non-satisfiability/mismatch-exclude-newer/pixi.toml covers “lock solved without exclude-newer, environment has it”.
  - tests/data/non-satisfiability/mismatch-exclude-newer2/pixi.toml stays as its own fixture, paired with its own lockfile.
  - The snapshots for both cases currently assert the locked package timestamp is newer than the environment cutoff:
      - crates/pixi_core/src/lock_file/satisfiability/snapshots/pixi_core__lock_file__satisfiability__tests__failing_satisfiability@mismatch-exclude-newer.snap
      - crates/pixi_core/src/lock_file/satisfiability/snapshots/pixi_core__lock_file__satisfiability__tests__failing_satisfiability@mismatch-exclude-newer2.snap

  Incidental Uses

  - crates/pixi/tests/integration_rust/install_tests.rs:977 uses exclude-newer only to stabilize a setuptools-related scenario.
  - crates/pixi/tests/integration_rust/upgrade_tests.rs:107 and crates/pixi/tests/integration_rust/upgrade_tests.rs:158 set exclude-newer, but the real subject is upgrade manifest rewriting.