[mshanemc]

What does this PR do?

• Centralize source-tracking environment settings in an Effect config loader with Effect Config.Boolean parsing, stricter numeric validation, fallback warnings, and legacy aliases.
• Cache one process-wide settings snapshot and provide it to local, remote, and Git Effect operations.
• Allow tests to inject a ConfigProvider or explicit config service instead of mutating global environment.

Configuration compatibility inventory

Compared against the installed Kit Env.getNumber/Env.getBoolean implementation and the previous source-tracking call sites. This PR is stacked on #888, which already migrated several reads to Effect; differences specific to that base are called out below.

Numeric input: stricter than Kit

Kit uses Lodash toNumber, without field-specific range/integer validation. The new config rejects the following inputs and uses the setting's default:

Input	Kit parsing	New config
Hexadecimal (0x10), binary (0b10), octal (0o10)	16, 2, 8	Default; validation warning
Infinity, -Infinity, or overflow such as 1e309	Non-finite number	Default; validation warning
NaN or malformed text such as bad	NaN, or the supplied default if one was passed to getNumber	Default; validation warning
Whitespace-only (" ")	0	Default; validation warning
Surrounding whitespace (" 12 ")	12	Default; validation warning
Literal empty string ("")	Absent/default	Still absent/default with the normal environment provider; no warning. If an injected provider preserves empty strings, validation warns and defaults.

Decimal forms such as +12, 01, and 1e2 remain accepted when their decoded value satisfies the field's constraints. We are not restricting all numbers to digit-only strings.

Field-specific validation and defaults

Setting	Accepted value	Invalid/missing fallback
SF_SOURCE_TRACKING_FD_PERMITS	Positive safe integer (1 through Number.MAX_SAFE_INTEGER)	64 on Windows; 256 elsewhere
SF_SOURCE_TRACKING_LOCK_TIMEOUT_SECONDS	Finite number greater than zero; fractions allowed	600 seconds
SF_SOURCE_TRACKING_LOCK_AUTOCLEAR_SECONDS	Finite number greater than zero; fractions allowed	300 seconds
SF_SOURCE_MEMBER_POLLING_TIMEOUT	Finite number greater than zero; fractions allowed	Size-based timeout: Math.ceil(memberCount * 0.05) + 5 seconds; empty-result limit 120
SF_SOURCE_TRACKING_FILE_VERSION	Non-negative safe integer, including zero	0

• Negative numbers are rejected for all numeric settings. Zero is rejected for permits and timeouts, but remains valid for file version.
• Fractional values are rejected for permits and file version, not for timeouts. Integers outside JavaScript's safe-integer range are rejected for permits and file version; finite timeout values do not have that safe-integer restriction.
• Kit parsed negative, zero, fractional, and unsafe-integer values without these field checks. Some callers already imposed additional behavior: the old overall polling timeout ignored non-positive overrides, but its separately calculated empty-result limit could still become zero, negative, or NaN. Config now rejects the override consistently for both settings.
• File version is still not an enum: other valid non-negative safe integers remain accepted. Only 1 selects the v1 format; other accepted values continue to select the legacy format. Rejecting negative/fractional values normally changes the warning/defaulting, not the selected format.

Legacy aliases and batching

• Polling retains SFDX_DISABLE_SOURCE_MEMBER_POLLING and SFDX_SOURCE_MEMBER_POLLING_TIMEOUT as deprecated aliases for their SF_ equivalents. These were supported by Core's Kit-based environment handling; this PR restores explicit alias handling relative to feat(git): replace isomorphic-git with Effect Git - W-22711959 #888's base.
• SF_SOURCE_TRACKING_BATCH_SIZE, then SFDX_SOURCE_TRACKING_BATCH_SIZE, are deprecated aliases for SF_SOURCE_TRACKING_FD_PERMITS. They now limit concurrent file descriptors rather than isomorphic-git batch length. Alias values are validated as positive safe integers and capped at 64 on Windows / 256 elsewhere. Smaller values remain effective; an explicit valid SF_SOURCE_TRACKING_FD_PERMITS is not capped.
• The old Kit batch-size defaults were 8000 on Windows / 15000 elsewhere. The FD-permit setting and its 64/256 defaults already exist in feat(git): replace isomorphic-git with Effect Git - W-22711959 #888; this PR adds the legacy aliases and their cap, rather than introducing the new Git engine/concurrency model.
• A present, non-empty canonical value wins even when invalid: it warns and uses the default instead of selecting an alias. In particular, old nested Kit batch-size reads could use the legacy value as the fallback for a malformed canonical batch-size value. Empty canonical values count as absent, allowing an alias.
• Selecting a deprecated alias emits a lifecycle warning. An explicitly configured FD-permit value also warns when it causes a legacy batch-size setting to be ignored.

Booleans, warnings, and evaluation timing

• Boolean settings use Effect Config.Boolean: lowercase true/false, yes/no, on/off, y/n, and 1/0. Compared with Kit, mixed-case words such as TRUE no longer parse (they warn and default to false); yes/on/y now mean true, and no/off/n are accepted as false. Invalid non-empty values warn and default to false.
• Relative to feat(git): replace isomorphic-git with Effect Git - W-22711959 #888, SF_SOURCE_TRACKING_INTEGRITY_CHECK now uses the same Config.Boolean literals instead of enabling only for exact lowercase true: lowercase yes/on/y/1 also enable it. Uppercase TRUE is invalid and defaults to false with a warning.
• Validation/deprecation warnings use Lifecycle.emitWarning, not Effect's console logger. Core may emit a Node process warning when no lifecycle warning listener is installed.
• All settings are loaded together and cached once, lazily on first process-runtime execution. Later environment mutations do not change settings or repeat their validation warnings. Previously several settings were read per operation, while batch size and the empty-poll limit were captured at module load. Invalid settings can now warn even if that operation does not use them.
• Provider/source errors still fail rather than being mistaken for invalid values and silently defaulted.

What was already enforced on #888's base

• Numeric environment parsing already used Effect's stricter string syntax at several call sites. Hex/binary/octal/whitespace rejection is a difference from Kit, not universally a new difference introduced by this PR.
• Lock timeout/autoclear already rejected non-finite and non-positive values and used the same defaults. This PR centralizes that behavior and adds lifecycle validation warnings.
• FD permits already had positive-integer schema validation, but invalid values reaching that schema could fail repository construction. This PR recovers invalid config to the platform default with a warning.
• Invalid file-version text could fail the tracking-file write through Effect.orDie; this PR warns and uses version 0 instead.
• Normal polling behavior is unchanged: one-second interval; count-driven overall timeout when no valid override is configured; 120 consecutive empty results after some results arrive, or a limit derived from a valid configured timeout. These decisions now live in config rather than in consumers.

Verification: exercised the installed Kit and current config loader with radix-prefixed numbers, infinities, NaN, malformed text, empty/whitespace strings, signed/leading-zero/scientific decimal forms, fractions, negatives, zero, unsafe integers, and boolean spellings.

What issues does this PR fix or reference?

@W-22711959@