feat: FOREST_PATH env variable

[LesnyRumcajs]

Summary of changes

Changes introduced in this pull request:

• exposes FOREST_PATH env variable to specify the DATA_DIR.
• honor this path across our binaries

Reference issue to close (if applicable)

Closes #6008

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

Release Notes

• New Features

  • Added FOREST_PATH environment variable to override the Forest data directory. Takes precedence over config file settings and defaults.
  • Data directory path is now logged when the daemon starts.

• Documentation

  • Updated environment variables reference guide with formatting improvements.
  • Added changelog entry documenting the FOREST_PATH environment variable.

[coderabbitai]

Walkthrough

Introduces FOREST_PATH as an environment variable to override the Forest data directory (precedence: env > config > default). The config-loading path in cli_shared is updated to apply this override, new helper functions default_data_dir() and default_token_path() are exposed, and all proofs-cache and RPC-token call sites are updated. Shell test scripts rename the existing FOREST_PATH daemon-binary variable to FOREST_DAEMON_PATH to avoid collision. Daemon startup now logs the resolved data directory.

Changes

FOREST_PATH data directory override

Layer / File(s)	Summary
Core env var constant, config override, and helper functions src/cli_shared/mod.rs, src/cli_shared/cli/client.rs	Defines FOREST_DATA_DIR_ENV ("FOREST_PATH") and RPC_TOKEN_FILENAME constants; read_config overwrites config.client.data_dir from the env var when set and non-empty; adds default_data_dir() and default_token_path() helpers and serial unit tests for env precedence and empty-value fallback.
RPC client token path resolution src/rpc/client.rs	Client::default_or_from_env now calls cli_shared::default_token_path() for the default token path, inheriting FOREST_PATH awareness; adds a test that writes a token file into a FOREST_PATH-pointed temp directory and verifies it is loaded.
Proofs cache dir callsites src/dev/subcommands/mod.rs, src/tool/offline_server/server.rs, src/tool/subcommands/api_cmd/api_compare_tests.rs, src/tool/subcommands/api_cmd/test_snapshot.rs, src/tool/subcommands/snapshot_cmd.rs	Replaces Config::default().client.data_dir with cli_shared::default_data_dir() in all maybe_set_proofs_parameter_cache_dir_env call sites so the proofs cache directory also honors FOREST_PATH.
Daemon startup logging and integration test src/daemon/mod.rs, tests/config.rs	Adds an info! log of config.client.data_dir in startup_init; adds an integration test asserting that setting FOREST_PATH to a non-existent path causes the daemon to create that directory.
Shell script variable rename scripts/tests/harness.sh, scripts/tests/butterflynet_check.sh, scripts/tests/calibnet_*.sh	Renames the exported daemon-binary variable from FOREST_PATH to FOREST_DAEMON_PATH in harness.sh and updates all daemon launch invocations across all test scripts to use the new name, freeing FOREST_PATH for the new env var meaning.
Changelog and env var docs CHANGELOG.md, docs/docs/users/reference/env_variables.md	Adds a changelog entry for FOREST_PATH and updates markdown formatting of the environment variables reference table.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• ChainSafe/forest#5836: The new api test-stateful subcommand constructs its RPC client via rpc::Client::default_or_from_env(None), which this PR updates to use default_token_path() and honor FOREST_PATH.
• ChainSafe/forest#6372: Both PRs touch the FIL_PROOFS_PARAMETER_CACHE environment setup; the retrieved PR updates params-caching in CI while this PR changes how the source path for that setup is derived via default_data_dir().

Suggested reviewers

• hanabi1224
• akaladarshi

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: introducing the FOREST_PATH environment variable feature for customizing the Forest data directory.
Linked Issues check	✅ Passed	The PR fully addresses issue #6008: implements FOREST_PATH env variable with proper precedence (env > config > defaults), updates test scripts to use FOREST_DAEMON_PATH, updates documentation, and ensures consistency across forest binaries.
Out of Scope Changes check	✅ Passed	All changes are directly related to implementing FOREST_PATH functionality and updating test scripts accordingly; no unrelated changes detected.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch forest-path-env-var

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch forest-path-env-var

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[codecov]

Codecov Report

❌ Patch coverage is 93.87755% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.42%. Comparing base (ead4de9) to head (37d8d93).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/daemon/mod.rs	0.00%	0 Missing and 1 partial ⚠️
src/tool/offline_server/server.rs	0.00%	1 Missing ⚠️
src/tool/subcommands/snapshot_cmd.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/cli_shared/cli/client.rs	100.00% <100.00%> (ø)
src/cli_shared/mod.rs	97.29% <100.00%> (+1.94%)	⬆️
src/dev/subcommands/mod.rs	73.52% <100.00%> (ø)
src/rpc/client.rs	56.48% <100.00%> (+3.34%)	⬆️
src/tool/subcommands/api_cmd/test_snapshot.rs	82.09% <100.00%> (ø)
src/daemon/mod.rs	24.70% <0.00%> (-0.04%)	⬇️
src/tool/offline_server/server.rs	27.23% <0.00%> (ø)
src/tool/subcommands/snapshot_cmd.rs	0.00% <0.00%> (ø)

... and 13 files with indirect coverage changes

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