fix(driver): validate and apply lint fixes through the OPY provider

[e54-bot]

Summary

wright lint --fix on a provider-backed OPY project reported duplicate-condition with fix: null: the mapped Program registered the provider's file table but retained no source text, and the dead-branch scanner only understood Workshop Else If/Else/End keywords. Two changes close the gap:

• After SourceMap::apply, the session retains each mapped member's authored text (Program::set_file_source, pinned workshop-rs rev 6a97b5c), so Program::source resolves for source extents, identity preconditions, and previews.
• dead_branch_fix prefers the chain markers' authored action spans — if/elif/else keywords and End at the dedent boundary, emitted by opy-rs since feat(lowering): attribute if-chain markers to authored keyword spans opy-rs#504 — and keeps the Workshop text scanner as fallback for marker-less programs.

Mapped fixes materialize as SourceEdits naming the member's file:// URI under the authored text's identity, then validate through the existing provider pipeline (lpp/validateEdits + lpp/check) instead of the raw Workshop reparse; write_previews resolves URI sources before its atomic replace. Unmapped artifacts carry no fix, and provider-side failures surface as structured refusals.

The dependency commit also folds in the pinned rev's catalog-spelling-near-miss classification (workshop-rs#406), mapped to unsupported with the other uncatalogued residuals.

Fixes #583

Test plan

• mapped_lint_fix_validates_and_writes_through_the_provider — fake LPP provider + injected marker map: preview names the authored member with full original/fixed OPY text, lpp/validateEdits and lpp/check are exercised, --write applies and re-lints clean
• Mapped-source retention hardened the span validation (invalid-span against retained text); mapped_lint_session fixtures now write the mapped text as the member
• Real opy-provider end-to-end: lint --fix previews and --write removes a duplicate elif across elif→elif, elif→else, and elif→dedent boundaries, including nested blocks
• Raw Workshop lint --fix/--write regression pass (lint_fix, lint_fixes, cli suites)
• cargo fmt --all -- --check, cargo clippy --workspace --all-targets --all-features -- -D warnings, cargo test --workspace --all-targets --all-features

[e54-bot]

CI classification for the Metrics drift failure (job 113952798102): the run installs OPY provider 0.3.6 against a baseline recorded on 0.3.0 (OPY provider differs: baseline=0.3.0 run=0.3.6), then every agent op on bastion and overwatch-ai-pve is skipped with parse-error and the CLI metrics collapse (e.g. bastion/cli:compile tokens 110371.0 -> 103.8, counts.* -> None). This is not a shared provider/baseline drift: the same job passes on a branch based on current main, so the parse errors are specific to this branch. The head is based on 78a3a0e, two commits behind main — 8317ca1 (#599, service check/compile without a canonical snapshot prewarm) touches the same service load path the agent ops use. Updating the branch onto current main would isolate whether the breakage comes from the stale base or from the change itself.