0056: Fixed internal safeguards and Rust patterns

Esdieff uses fixed internal safeguards for input size and depth, reference expansion, processing work and report growth. There is no established caller need for configurable processing budgets. Remove the public Limits type, quota setters and quota-selecting constructors instead of carrying implementation choices into the caller’s interface. Semantic request options remain public. This supersedes the configurability requirement in ADR 0009: Bounded processing and reporting. Its distinction between unfinished work, invalid models and omitted report details remains in force.

Numeric comparison of admitted exact values uses their bounded representation directly. NumberWork remains an internal operation counter, and public comparison needs no caller-owned work allowance. Location accessors also use the fixed internal pointer ceiling without requiring callers to supply bytes.

Use pinned corvus-regex-ecma262 0.2.7 for Unicode u syntax and unanchored matching, including Model checking, Sample-value checking, Generation and Recorded trace checking. Retain the qualified guards for names, escape spelling, decimal endpoints and the fixed supplied-size/structure ceilings. An explicit 100 ms cooperative backtracking timeout is attached to each compiled expression. Corvus additionally enforces its compilation-size and backtracking-state capacities. Unknown/unsupported capabilities and capacity or timeout exhaustion leave affected work unfinished. Neither establishes invalid syntax or mismatch.

Compile and match directly through the supported Rust API, without a toolkit pattern worker, JavaScript runtime, custom allocator or helper executable. Independent calls do not share spent polling or duration allowances. The engine may reuse thread-local working storage according to its own capacity policy. A completed or exhausted call does not poison later calls. This supersedes ADR 0014: Bounded partial ECMAScript pattern capability and the worker/allocation decisions of ADR 0028: Bounded effective model pattern syntax and ADR 0045: One pattern engine per trace or generation request. The effective scopes, source locations and incomplete-result semantics of ADR 0028 remain unchanged.

The timeout is an internal policy, not a universal deadline. Some linear search paths finish without consulting it, parsing and compilation are not externally cancellable, and a batch can take proportionally longer. There is no exact per-request memory, resident-memory or instruction-count guarantee. Existing fixed internal counters remain useful protections, without claiming to account for engine-private allocations.

Considered options

Preserving QuickJS heap, JavaScript stack, worker-stack and interrupt settings would constrain the replacement to implementation details without a demonstrated caller benefit. A patched engine or supervised helper would add ongoing maintenance, packaging and platform complexity. Corvus supplies the safeguards needed for the current workflows through its released API. Rust regex lacks the required lookaround/backreference semantics, while jlens-regress would require more custom control and syntax integration. Strict host isolation and a new public resource-budget interface are outside this decision.